1 /*
2 * Copyright (c) 2001, 2012, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #include "precompiled.hpp"
26 #include "code/icBuffer.hpp"
27 #include "gc_implementation/g1/bufferingOopClosure.hpp"
28 #include "gc_implementation/g1/concurrentG1Refine.hpp"
29 #include "gc_implementation/g1/concurrentG1RefineThread.hpp"
30 #include "gc_implementation/g1/concurrentMarkThread.inline.hpp"
31 #include "gc_implementation/g1/g1AllocRegion.inline.hpp"
32 #include "gc_implementation/g1/g1CollectedHeap.inline.hpp"
33 #include "gc_implementation/g1/g1CollectorPolicy.hpp"
34 #include "gc_implementation/g1/g1ErgoVerbose.hpp"
35 #include "gc_implementation/g1/g1EvacFailure.hpp"
36 #include "gc_implementation/g1/g1GCPhaseTimes.hpp"
37 #include "gc_implementation/g1/g1Log.hpp"
38 #include "gc_implementation/g1/g1MarkSweep.hpp"
39 #include "gc_implementation/g1/g1OopClosures.inline.hpp"
40 #include "gc_implementation/g1/g1RemSet.inline.hpp"
41 #include "gc_implementation/g1/heapRegion.inline.hpp"
42 #include "gc_implementation/g1/heapRegionRemSet.hpp"
43 #include "gc_implementation/g1/heapRegionSeq.inline.hpp"
44 #include "gc_implementation/g1/vm_operations_g1.hpp"
45 #include "gc_implementation/shared/isGCActiveMark.hpp"
46 #include "memory/gcLocker.inline.hpp"
47 #include "memory/genOopClosures.inline.hpp"
48 #include "memory/generationSpec.hpp"
49 #include "memory/referenceProcessor.hpp"
50 #include "oops/oop.inline.hpp"
51 #include "oops/oop.pcgc.inline.hpp"
52 #include "runtime/aprofiler.hpp"
53 #include "runtime/vmThread.hpp"
54
55 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0;
56
57 // turn it on so that the contents of the young list (scan-only /
58 // to-be-collected) are printed at "strategic" points before / during
59 // / after the collection --- this is useful for debugging
60 #define YOUNG_LIST_VERBOSE 0
61 // CURRENT STATUS
62 // This file is under construction. Search for "FIXME".
63
64 // INVARIANTS/NOTES
65 //
66 // All allocation activity covered by the G1CollectedHeap interface is
67 // serialized by acquiring the HeapLock. This happens in mem_allocate
68 // and allocate_new_tlab, which are the "entry" points to the
69 // allocation code from the rest of the JVM. (Note that this does not
70 // apply to TLAB allocation, which is not part of this interface: it
71 // is done by clients of this interface.)
72
73 // Notes on implementation of parallelism in different tasks.
74 //
75 // G1ParVerifyTask uses heap_region_par_iterate_chunked() for parallelism.
76 // The number of GC workers is passed to heap_region_par_iterate_chunked().
77 // It does use run_task() which sets _n_workers in the task.
78 // G1ParTask executes g1_process_strong_roots() ->
79 // SharedHeap::process_strong_roots() which calls eventuall to
80 // CardTableModRefBS::par_non_clean_card_iterate_work() which uses
81 // SequentialSubTasksDone. SharedHeap::process_strong_roots() also
82 // directly uses SubTasksDone (_process_strong_tasks field in SharedHeap).
83 //
84
85 // Local to this file.
86
87 class RefineCardTableEntryClosure: public CardTableEntryClosure {
88 SuspendibleThreadSet* _sts;
89 G1RemSet* _g1rs;
90 ConcurrentG1Refine* _cg1r;
91 bool _concurrent;
92 public:
93 RefineCardTableEntryClosure(SuspendibleThreadSet* sts,
94 G1RemSet* g1rs,
95 ConcurrentG1Refine* cg1r) :
96 _sts(sts), _g1rs(g1rs), _cg1r(cg1r), _concurrent(true)
97 {}
98 bool do_card_ptr(jbyte* card_ptr, int worker_i) {
99 bool oops_into_cset = _g1rs->concurrentRefineOneCard(card_ptr, worker_i, false);
100 // This path is executed by the concurrent refine or mutator threads,
101 // concurrently, and so we do not care if card_ptr contains references
102 // that point into the collection set.
103 assert(!oops_into_cset, "should be");
104
105 if (_concurrent && _sts->should_yield()) {
106 // Caller will actually yield.
107 return false;
108 }
109 // Otherwise, we finished successfully; return true.
110 return true;
111 }
112 void set_concurrent(bool b) { _concurrent = b; }
113 };
114
115
116 class ClearLoggedCardTableEntryClosure: public CardTableEntryClosure {
117 int _calls;
118 G1CollectedHeap* _g1h;
119 CardTableModRefBS* _ctbs;
120 int _histo[256];
121 public:
122 ClearLoggedCardTableEntryClosure() :
123 _calls(0)
124 {
125 _g1h = G1CollectedHeap::heap();
126 _ctbs = (CardTableModRefBS*)_g1h->barrier_set();
127 for (int i = 0; i < 256; i++) _histo[i] = 0;
128 }
129 bool do_card_ptr(jbyte* card_ptr, int worker_i) {
130 if (_g1h->is_in_reserved(_ctbs->addr_for(card_ptr))) {
131 _calls++;
132 unsigned char* ujb = (unsigned char*)card_ptr;
133 int ind = (int)(*ujb);
134 _histo[ind]++;
135 *card_ptr = -1;
136 }
137 return true;
138 }
139 int calls() { return _calls; }
140 void print_histo() {
141 gclog_or_tty->print_cr("Card table value histogram:");
142 for (int i = 0; i < 256; i++) {
143 if (_histo[i] != 0) {
144 gclog_or_tty->print_cr(" %d: %d", i, _histo[i]);
145 }
146 }
147 }
148 };
149
150 class RedirtyLoggedCardTableEntryClosure: public CardTableEntryClosure {
151 int _calls;
152 G1CollectedHeap* _g1h;
153 CardTableModRefBS* _ctbs;
154 public:
155 RedirtyLoggedCardTableEntryClosure() :
156 _calls(0)
157 {
158 _g1h = G1CollectedHeap::heap();
159 _ctbs = (CardTableModRefBS*)_g1h->barrier_set();
160 }
161 bool do_card_ptr(jbyte* card_ptr, int worker_i) {
162 if (_g1h->is_in_reserved(_ctbs->addr_for(card_ptr))) {
163 _calls++;
164 *card_ptr = 0;
165 }
166 return true;
167 }
168 int calls() { return _calls; }
169 };
170
171 class RedirtyLoggedCardTableEntryFastClosure : public CardTableEntryClosure {
172 public:
173 bool do_card_ptr(jbyte* card_ptr, int worker_i) {
174 *card_ptr = CardTableModRefBS::dirty_card_val();
175 return true;
176 }
177 };
178
179 YoungList::YoungList(G1CollectedHeap* g1h) :
180 _g1h(g1h), _head(NULL), _length(0), _last_sampled_rs_lengths(0),
181 _survivor_head(NULL), _survivor_tail(NULL), _survivor_length(0) {
182 guarantee(check_list_empty(false), "just making sure...");
183 }
184
185 void YoungList::push_region(HeapRegion *hr) {
186 assert(!hr->is_young(), "should not already be young");
187 assert(hr->get_next_young_region() == NULL, "cause it should!");
188
189 hr->set_next_young_region(_head);
190 _head = hr;
191
192 _g1h->g1_policy()->set_region_eden(hr, (int) _length);
193 ++_length;
194 }
195
196 void YoungList::add_survivor_region(HeapRegion* hr) {
197 assert(hr->is_survivor(), "should be flagged as survivor region");
198 assert(hr->get_next_young_region() == NULL, "cause it should!");
199
200 hr->set_next_young_region(_survivor_head);
201 if (_survivor_head == NULL) {
202 _survivor_tail = hr;
203 }
204 _survivor_head = hr;
205 ++_survivor_length;
206 }
207
208 void YoungList::empty_list(HeapRegion* list) {
209 while (list != NULL) {
210 HeapRegion* next = list->get_next_young_region();
211 list->set_next_young_region(NULL);
212 list->uninstall_surv_rate_group();
213 list->set_not_young();
214 list = next;
215 }
216 }
217
218 void YoungList::empty_list() {
219 assert(check_list_well_formed(), "young list should be well formed");
220
221 empty_list(_head);
222 _head = NULL;
223 _length = 0;
224
225 empty_list(_survivor_head);
226 _survivor_head = NULL;
227 _survivor_tail = NULL;
228 _survivor_length = 0;
229
230 _last_sampled_rs_lengths = 0;
231
232 assert(check_list_empty(false), "just making sure...");
233 }
234
235 bool YoungList::check_list_well_formed() {
236 bool ret = true;
237
238 uint length = 0;
239 HeapRegion* curr = _head;
240 HeapRegion* last = NULL;
241 while (curr != NULL) {
242 if (!curr->is_young()) {
243 gclog_or_tty->print_cr("### YOUNG REGION "PTR_FORMAT"-"PTR_FORMAT" "
244 "incorrectly tagged (y: %d, surv: %d)",
245 curr->bottom(), curr->end(),
246 curr->is_young(), curr->is_survivor());
247 ret = false;
248 }
249 ++length;
250 last = curr;
251 curr = curr->get_next_young_region();
252 }
253 ret = ret && (length == _length);
254
255 if (!ret) {
256 gclog_or_tty->print_cr("### YOUNG LIST seems not well formed!");
257 gclog_or_tty->print_cr("### list has %u entries, _length is %u",
258 length, _length);
259 }
260
261 return ret;
262 }
263
264 bool YoungList::check_list_empty(bool check_sample) {
265 bool ret = true;
266
267 if (_length != 0) {
268 gclog_or_tty->print_cr("### YOUNG LIST should have 0 length, not %u",
269 _length);
270 ret = false;
271 }
272 if (check_sample && _last_sampled_rs_lengths != 0) {
273 gclog_or_tty->print_cr("### YOUNG LIST has non-zero last sampled RS lengths");
274 ret = false;
275 }
276 if (_head != NULL) {
277 gclog_or_tty->print_cr("### YOUNG LIST does not have a NULL head");
278 ret = false;
279 }
280 if (!ret) {
281 gclog_or_tty->print_cr("### YOUNG LIST does not seem empty");
282 }
283
284 return ret;
285 }
286
287 void
288 YoungList::rs_length_sampling_init() {
289 _sampled_rs_lengths = 0;
290 _curr = _head;
291 }
292
293 bool
294 YoungList::rs_length_sampling_more() {
295 return _curr != NULL;
296 }
297
298 void
299 YoungList::rs_length_sampling_next() {
300 assert( _curr != NULL, "invariant" );
301 size_t rs_length = _curr->rem_set()->occupied();
302
303 _sampled_rs_lengths += rs_length;
304
305 // The current region may not yet have been added to the
306 // incremental collection set (it gets added when it is
307 // retired as the current allocation region).
308 if (_curr->in_collection_set()) {
309 // Update the collection set policy information for this region
310 _g1h->g1_policy()->update_incremental_cset_info(_curr, rs_length);
311 }
312
313 _curr = _curr->get_next_young_region();
314 if (_curr == NULL) {
315 _last_sampled_rs_lengths = _sampled_rs_lengths;
316 // gclog_or_tty->print_cr("last sampled RS lengths = %d", _last_sampled_rs_lengths);
317 }
318 }
319
320 void
321 YoungList::reset_auxilary_lists() {
322 guarantee( is_empty(), "young list should be empty" );
323 assert(check_list_well_formed(), "young list should be well formed");
324
325 // Add survivor regions to SurvRateGroup.
326 _g1h->g1_policy()->note_start_adding_survivor_regions();
327 _g1h->g1_policy()->finished_recalculating_age_indexes(true /* is_survivors */);
328
329 int young_index_in_cset = 0;
330 for (HeapRegion* curr = _survivor_head;
331 curr != NULL;
332 curr = curr->get_next_young_region()) {
333 _g1h->g1_policy()->set_region_survivor(curr, young_index_in_cset);
334
335 // The region is a non-empty survivor so let's add it to
336 // the incremental collection set for the next evacuation
337 // pause.
338 _g1h->g1_policy()->add_region_to_incremental_cset_rhs(curr);
339 young_index_in_cset += 1;
340 }
341 assert((uint) young_index_in_cset == _survivor_length, "post-condition");
342 _g1h->g1_policy()->note_stop_adding_survivor_regions();
343
344 _head = _survivor_head;
345 _length = _survivor_length;
346 if (_survivor_head != NULL) {
347 assert(_survivor_tail != NULL, "cause it shouldn't be");
348 assert(_survivor_length > 0, "invariant");
349 _survivor_tail->set_next_young_region(NULL);
350 }
351
352 // Don't clear the survivor list handles until the start of
353 // the next evacuation pause - we need it in order to re-tag
354 // the survivor regions from this evacuation pause as 'young'
355 // at the start of the next.
356
357 _g1h->g1_policy()->finished_recalculating_age_indexes(false /* is_survivors */);
358
359 assert(check_list_well_formed(), "young list should be well formed");
360 }
361
362 void YoungList::print() {
363 HeapRegion* lists[] = {_head, _survivor_head};
364 const char* names[] = {"YOUNG", "SURVIVOR"};
365
366 for (unsigned int list = 0; list < ARRAY_SIZE(lists); ++list) {
367 gclog_or_tty->print_cr("%s LIST CONTENTS", names[list]);
368 HeapRegion *curr = lists[list];
369 if (curr == NULL)
370 gclog_or_tty->print_cr(" empty");
371 while (curr != NULL) {
372 gclog_or_tty->print_cr(" "HR_FORMAT", P: "PTR_FORMAT "N: "PTR_FORMAT", age: %4d",
373 HR_FORMAT_PARAMS(curr),
374 curr->prev_top_at_mark_start(),
375 curr->next_top_at_mark_start(),
376 curr->age_in_surv_rate_group_cond());
377 curr = curr->get_next_young_region();
378 }
379 }
380
381 gclog_or_tty->print_cr("");
382 }
383
384 void G1CollectedHeap::push_dirty_cards_region(HeapRegion* hr)
385 {
386 // Claim the right to put the region on the dirty cards region list
387 // by installing a self pointer.
388 HeapRegion* next = hr->get_next_dirty_cards_region();
389 if (next == NULL) {
390 HeapRegion* res = (HeapRegion*)
391 Atomic::cmpxchg_ptr(hr, hr->next_dirty_cards_region_addr(),
392 NULL);
393 if (res == NULL) {
394 HeapRegion* head;
395 do {
396 // Put the region to the dirty cards region list.
397 head = _dirty_cards_region_list;
398 next = (HeapRegion*)
399 Atomic::cmpxchg_ptr(hr, &_dirty_cards_region_list, head);
400 if (next == head) {
401 assert(hr->get_next_dirty_cards_region() == hr,
402 "hr->get_next_dirty_cards_region() != hr");
403 if (next == NULL) {
404 // The last region in the list points to itself.
405 hr->set_next_dirty_cards_region(hr);
406 } else {
407 hr->set_next_dirty_cards_region(next);
408 }
409 }
410 } while (next != head);
411 }
412 }
413 }
414
415 HeapRegion* G1CollectedHeap::pop_dirty_cards_region()
416 {
417 HeapRegion* head;
418 HeapRegion* hr;
419 do {
420 head = _dirty_cards_region_list;
421 if (head == NULL) {
422 return NULL;
423 }
424 HeapRegion* new_head = head->get_next_dirty_cards_region();
425 if (head == new_head) {
426 // The last region.
427 new_head = NULL;
428 }
429 hr = (HeapRegion*)Atomic::cmpxchg_ptr(new_head, &_dirty_cards_region_list,
430 head);
431 } while (hr != head);
432 assert(hr != NULL, "invariant");
433 hr->set_next_dirty_cards_region(NULL);
434 return hr;
435 }
436
437 void G1CollectedHeap::stop_conc_gc_threads() {
438 _cg1r->stop();
439 _cmThread->stop();
440 }
441
442 #ifdef ASSERT
443 // A region is added to the collection set as it is retired
444 // so an address p can point to a region which will be in the
445 // collection set but has not yet been retired. This method
446 // therefore is only accurate during a GC pause after all
447 // regions have been retired. It is used for debugging
448 // to check if an nmethod has references to objects that can
449 // be move during a partial collection. Though it can be
450 // inaccurate, it is sufficient for G1 because the conservative
451 // implementation of is_scavengable() for G1 will indicate that
452 // all nmethods must be scanned during a partial collection.
453 bool G1CollectedHeap::is_in_partial_collection(const void* p) {
454 HeapRegion* hr = heap_region_containing(p);
455 return hr != NULL && hr->in_collection_set();
456 }
457 #endif
458
459 // Returns true if the reference points to an object that
460 // can move in an incremental collecction.
461 bool G1CollectedHeap::is_scavengable(const void* p) {
462 G1CollectedHeap* g1h = G1CollectedHeap::heap();
463 G1CollectorPolicy* g1p = g1h->g1_policy();
464 HeapRegion* hr = heap_region_containing(p);
465 if (hr == NULL) {
466 // perm gen (or null)
467 return false;
468 } else {
469 return !hr->isHumongous();
470 }
471 }
472
473 void G1CollectedHeap::check_ct_logs_at_safepoint() {
474 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
475 CardTableModRefBS* ct_bs = (CardTableModRefBS*)barrier_set();
476
477 // Count the dirty cards at the start.
478 CountNonCleanMemRegionClosure count1(this);
479 ct_bs->mod_card_iterate(&count1);
480 int orig_count = count1.n();
481
482 // First clear the logged cards.
483 ClearLoggedCardTableEntryClosure clear;
484 dcqs.set_closure(&clear);
485 dcqs.apply_closure_to_all_completed_buffers();
486 dcqs.iterate_closure_all_threads(false);
487 clear.print_histo();
488
489 // Now ensure that there's no dirty cards.
490 CountNonCleanMemRegionClosure count2(this);
491 ct_bs->mod_card_iterate(&count2);
492 if (count2.n() != 0) {
493 gclog_or_tty->print_cr("Card table has %d entries; %d originally",
494 count2.n(), orig_count);
495 }
496 guarantee(count2.n() == 0, "Card table should be clean.");
497
498 RedirtyLoggedCardTableEntryClosure redirty;
499 JavaThread::dirty_card_queue_set().set_closure(&redirty);
500 dcqs.apply_closure_to_all_completed_buffers();
501 dcqs.iterate_closure_all_threads(false);
502 gclog_or_tty->print_cr("Log entries = %d, dirty cards = %d.",
503 clear.calls(), orig_count);
504 guarantee(redirty.calls() == clear.calls(),
505 "Or else mechanism is broken.");
506
507 CountNonCleanMemRegionClosure count3(this);
508 ct_bs->mod_card_iterate(&count3);
509 if (count3.n() != orig_count) {
510 gclog_or_tty->print_cr("Should have restored them all: orig = %d, final = %d.",
511 orig_count, count3.n());
512 guarantee(count3.n() >= orig_count, "Should have restored them all.");
513 }
514
515 JavaThread::dirty_card_queue_set().set_closure(_refine_cte_cl);
516 }
517
518 // Private class members.
519
520 G1CollectedHeap* G1CollectedHeap::_g1h;
521
522 // Private methods.
523
524 HeapRegion*
525 G1CollectedHeap::new_region_try_secondary_free_list() {
526 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
527 while (!_secondary_free_list.is_empty() || free_regions_coming()) {
528 if (!_secondary_free_list.is_empty()) {
529 if (G1ConcRegionFreeingVerbose) {
530 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
531 "secondary_free_list has %u entries",
532 _secondary_free_list.length());
533 }
534 // It looks as if there are free regions available on the
535 // secondary_free_list. Let's move them to the free_list and try
536 // again to allocate from it.
537 append_secondary_free_list();
538
539 assert(!_free_list.is_empty(), "if the secondary_free_list was not "
540 "empty we should have moved at least one entry to the free_list");
541 HeapRegion* res = _free_list.remove_head();
542 if (G1ConcRegionFreeingVerbose) {
543 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
544 "allocated "HR_FORMAT" from secondary_free_list",
545 HR_FORMAT_PARAMS(res));
546 }
547 return res;
548 }
549
550 // Wait here until we get notifed either when (a) there are no
551 // more free regions coming or (b) some regions have been moved on
552 // the secondary_free_list.
553 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
554 }
555
556 if (G1ConcRegionFreeingVerbose) {
557 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
558 "could not allocate from secondary_free_list");
559 }
560 return NULL;
561 }
562
563 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool do_expand) {
564 assert(!isHumongous(word_size) || word_size <= HeapRegion::GrainWords,
565 "the only time we use this to allocate a humongous region is "
566 "when we are allocating a single humongous region");
567
568 HeapRegion* res;
569 if (G1StressConcRegionFreeing) {
570 if (!_secondary_free_list.is_empty()) {
571 if (G1ConcRegionFreeingVerbose) {
572 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
573 "forced to look at the secondary_free_list");
574 }
575 res = new_region_try_secondary_free_list();
576 if (res != NULL) {
577 return res;
578 }
579 }
580 }
581 res = _free_list.remove_head_or_null();
582 if (res == NULL) {
583 if (G1ConcRegionFreeingVerbose) {
584 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
585 "res == NULL, trying the secondary_free_list");
586 }
587 res = new_region_try_secondary_free_list();
588 }
589 if (res == NULL && do_expand && _expand_heap_after_alloc_failure) {
590 // Currently, only attempts to allocate GC alloc regions set
591 // do_expand to true. So, we should only reach here during a
592 // safepoint. If this assumption changes we might have to
593 // reconsider the use of _expand_heap_after_alloc_failure.
594 assert(SafepointSynchronize::is_at_safepoint(), "invariant");
595
596 ergo_verbose1(ErgoHeapSizing,
597 "attempt heap expansion",
598 ergo_format_reason("region allocation request failed")
599 ergo_format_byte("allocation request"),
600 word_size * HeapWordSize);
601 if (expand(word_size * HeapWordSize)) {
602 // Given that expand() succeeded in expanding the heap, and we
603 // always expand the heap by an amount aligned to the heap
604 // region size, the free list should in theory not be empty. So
605 // it would probably be OK to use remove_head(). But the extra
606 // check for NULL is unlikely to be a performance issue here (we
607 // just expanded the heap!) so let's just be conservative and
608 // use remove_head_or_null().
609 res = _free_list.remove_head_or_null();
610 } else {
611 _expand_heap_after_alloc_failure = false;
612 }
613 }
614 return res;
615 }
616
617 uint G1CollectedHeap::humongous_obj_allocate_find_first(uint num_regions,
618 size_t word_size) {
619 assert(isHumongous(word_size), "word_size should be humongous");
620 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
621
622 uint first = G1_NULL_HRS_INDEX;
623 if (num_regions == 1) {
624 // Only one region to allocate, no need to go through the slower
625 // path. The caller will attempt the expasion if this fails, so
626 // let's not try to expand here too.
627 HeapRegion* hr = new_region(word_size, false /* do_expand */);
628 if (hr != NULL) {
629 first = hr->hrs_index();
630 } else {
631 first = G1_NULL_HRS_INDEX;
632 }
633 } else {
634 // We can't allocate humongous regions while cleanupComplete() is
635 // running, since some of the regions we find to be empty might not
636 // yet be added to the free list and it is not straightforward to
637 // know which list they are on so that we can remove them. Note
638 // that we only need to do this if we need to allocate more than
639 // one region to satisfy the current humongous allocation
640 // request. If we are only allocating one region we use the common
641 // region allocation code (see above).
642 wait_while_free_regions_coming();
643 append_secondary_free_list_if_not_empty_with_lock();
644
645 if (free_regions() >= num_regions) {
646 first = _hrs.find_contiguous(num_regions);
647 if (first != G1_NULL_HRS_INDEX) {
648 for (uint i = first; i < first + num_regions; ++i) {
649 HeapRegion* hr = region_at(i);
650 assert(hr->is_empty(), "sanity");
651 assert(is_on_master_free_list(hr), "sanity");
652 hr->set_pending_removal(true);
653 }
654 _free_list.remove_all_pending(num_regions);
655 }
656 }
657 }
658 return first;
659 }
660
661 HeapWord*
662 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first,
663 uint num_regions,
664 size_t word_size) {
665 assert(first != G1_NULL_HRS_INDEX, "pre-condition");
666 assert(isHumongous(word_size), "word_size should be humongous");
667 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
668
669 // Index of last region in the series + 1.
670 uint last = first + num_regions;
671
672 // We need to initialize the region(s) we just discovered. This is
673 // a bit tricky given that it can happen concurrently with
674 // refinement threads refining cards on these regions and
675 // potentially wanting to refine the BOT as they are scanning
676 // those cards (this can happen shortly after a cleanup; see CR
677 // 6991377). So we have to set up the region(s) carefully and in
678 // a specific order.
679
680 // The word size sum of all the regions we will allocate.
681 size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords;
682 assert(word_size <= word_size_sum, "sanity");
683
684 // This will be the "starts humongous" region.
685 HeapRegion* first_hr = region_at(first);
686 // The header of the new object will be placed at the bottom of
687 // the first region.
688 HeapWord* new_obj = first_hr->bottom();
689 // This will be the new end of the first region in the series that
690 // should also match the end of the last region in the seriers.
691 HeapWord* new_end = new_obj + word_size_sum;
692 // This will be the new top of the first region that will reflect
693 // this allocation.
694 HeapWord* new_top = new_obj + word_size;
695
696 // First, we need to zero the header of the space that we will be
697 // allocating. When we update top further down, some refinement
698 // threads might try to scan the region. By zeroing the header we
699 // ensure that any thread that will try to scan the region will
700 // come across the zero klass word and bail out.
701 //
702 // NOTE: It would not have been correct to have used
703 // CollectedHeap::fill_with_object() and make the space look like
704 // an int array. The thread that is doing the allocation will
705 // later update the object header to a potentially different array
706 // type and, for a very short period of time, the klass and length
707 // fields will be inconsistent. This could cause a refinement
708 // thread to calculate the object size incorrectly.
709 Copy::fill_to_words(new_obj, oopDesc::header_size(), 0);
710
711 // We will set up the first region as "starts humongous". This
712 // will also update the BOT covering all the regions to reflect
713 // that there is a single object that starts at the bottom of the
714 // first region.
715 first_hr->set_startsHumongous(new_top, new_end);
716
717 // Then, if there are any, we will set up the "continues
718 // humongous" regions.
719 HeapRegion* hr = NULL;
720 for (uint i = first + 1; i < last; ++i) {
721 hr = region_at(i);
722 hr->set_continuesHumongous(first_hr);
723 }
724 // If we have "continues humongous" regions (hr != NULL), then the
725 // end of the last one should match new_end.
726 assert(hr == NULL || hr->end() == new_end, "sanity");
727
728 // Up to this point no concurrent thread would have been able to
729 // do any scanning on any region in this series. All the top
730 // fields still point to bottom, so the intersection between
731 // [bottom,top] and [card_start,card_end] will be empty. Before we
732 // update the top fields, we'll do a storestore to make sure that
733 // no thread sees the update to top before the zeroing of the
734 // object header and the BOT initialization.
735 OrderAccess::storestore();
736
737 // Now that the BOT and the object header have been initialized,
738 // we can update top of the "starts humongous" region.
739 assert(first_hr->bottom() < new_top && new_top <= first_hr->end(),
740 "new_top should be in this region");
741 first_hr->set_top(new_top);
742 if (_hr_printer.is_active()) {
743 HeapWord* bottom = first_hr->bottom();
744 HeapWord* end = first_hr->orig_end();
745 if ((first + 1) == last) {
746 // the series has a single humongous region
747 _hr_printer.alloc(G1HRPrinter::SingleHumongous, first_hr, new_top);
748 } else {
749 // the series has more than one humongous regions
750 _hr_printer.alloc(G1HRPrinter::StartsHumongous, first_hr, end);
751 }
752 }
753
754 // Now, we will update the top fields of the "continues humongous"
755 // regions. The reason we need to do this is that, otherwise,
756 // these regions would look empty and this will confuse parts of
757 // G1. For example, the code that looks for a consecutive number
758 // of empty regions will consider them empty and try to
759 // re-allocate them. We can extend is_empty() to also include
760 // !continuesHumongous(), but it is easier to just update the top
761 // fields here. The way we set top for all regions (i.e., top ==
762 // end for all regions but the last one, top == new_top for the
763 // last one) is actually used when we will free up the humongous
764 // region in free_humongous_region().
765 hr = NULL;
766 for (uint i = first + 1; i < last; ++i) {
767 hr = region_at(i);
768 if ((i + 1) == last) {
769 // last continues humongous region
770 assert(hr->bottom() < new_top && new_top <= hr->end(),
771 "new_top should fall on this region");
772 hr->set_top(new_top);
773 _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, new_top);
774 } else {
775 // not last one
776 assert(new_top > hr->end(), "new_top should be above this region");
777 hr->set_top(hr->end());
778 _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, hr->end());
779 }
780 }
781 // If we have continues humongous regions (hr != NULL), then the
782 // end of the last one should match new_end and its top should
783 // match new_top.
784 assert(hr == NULL ||
785 (hr->end() == new_end && hr->top() == new_top), "sanity");
786
787 assert(first_hr->used() == word_size * HeapWordSize, "invariant");
788 _summary_bytes_used += first_hr->used();
789 _humongous_set.add(first_hr);
790
791 return new_obj;
792 }
793
794 // If could fit into free regions w/o expansion, try.
795 // Otherwise, if can expand, do so.
796 // Otherwise, if using ex regions might help, try with ex given back.
797 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size) {
798 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
799
800 verify_region_sets_optional();
801
802 size_t word_size_rounded = round_to(word_size, HeapRegion::GrainWords);
803 uint num_regions = (uint) (word_size_rounded / HeapRegion::GrainWords);
804 uint x_num = expansion_regions();
805 uint fs = _hrs.free_suffix();
806 uint first = humongous_obj_allocate_find_first(num_regions, word_size);
807 if (first == G1_NULL_HRS_INDEX) {
808 // The only thing we can do now is attempt expansion.
809 if (fs + x_num >= num_regions) {
810 // If the number of regions we're trying to allocate for this
811 // object is at most the number of regions in the free suffix,
812 // then the call to humongous_obj_allocate_find_first() above
813 // should have succeeded and we wouldn't be here.
814 //
815 // We should only be trying to expand when the free suffix is
816 // not sufficient for the object _and_ we have some expansion
817 // room available.
818 assert(num_regions > fs, "earlier allocation should have succeeded");
819
820 ergo_verbose1(ErgoHeapSizing,
821 "attempt heap expansion",
822 ergo_format_reason("humongous allocation request failed")
823 ergo_format_byte("allocation request"),
824 word_size * HeapWordSize);
825 if (expand((num_regions - fs) * HeapRegion::GrainBytes)) {
826 // Even though the heap was expanded, it might not have
827 // reached the desired size. So, we cannot assume that the
828 // allocation will succeed.
829 first = humongous_obj_allocate_find_first(num_regions, word_size);
830 }
831 }
832 }
833
834 HeapWord* result = NULL;
835 if (first != G1_NULL_HRS_INDEX) {
836 result =
837 humongous_obj_allocate_initialize_regions(first, num_regions, word_size);
838 assert(result != NULL, "it should always return a valid result");
839
840 // A successful humongous object allocation changes the used space
841 // information of the old generation so we need to recalculate the
842 // sizes and update the jstat counters here.
843 g1mm()->update_sizes();
844 }
845
846 verify_region_sets_optional();
847
848 return result;
849 }
850
851 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) {
852 assert_heap_not_locked_and_not_at_safepoint();
853 assert(!isHumongous(word_size), "we do not allow humongous TLABs");
854
855 unsigned int dummy_gc_count_before;
856 return attempt_allocation(word_size, &dummy_gc_count_before);
857 }
858
859 HeapWord*
860 G1CollectedHeap::mem_allocate(size_t word_size,
861 bool* gc_overhead_limit_was_exceeded) {
862 assert_heap_not_locked_and_not_at_safepoint();
863
864 // Loop until the allocation is satisified, or unsatisfied after GC.
865 for (int try_count = 1; /* we'll return */; try_count += 1) {
866 unsigned int gc_count_before;
867
868 HeapWord* result = NULL;
869 if (!isHumongous(word_size)) {
870 result = attempt_allocation(word_size, &gc_count_before);
871 } else {
872 result = attempt_allocation_humongous(word_size, &gc_count_before);
873 }
874 if (result != NULL) {
875 return result;
876 }
877
878 // Create the garbage collection operation...
879 VM_G1CollectForAllocation op(gc_count_before, word_size);
880 // ...and get the VM thread to execute it.
881 VMThread::execute(&op);
882
883 if (op.prologue_succeeded() && op.pause_succeeded()) {
884 // If the operation was successful we'll return the result even
885 // if it is NULL. If the allocation attempt failed immediately
886 // after a Full GC, it's unlikely we'll be able to allocate now.
887 HeapWord* result = op.result();
888 if (result != NULL && !isHumongous(word_size)) {
889 // Allocations that take place on VM operations do not do any
890 // card dirtying and we have to do it here. We only have to do
891 // this for non-humongous allocations, though.
892 dirty_young_block(result, word_size);
893 }
894 return result;
895 } else {
896 assert(op.result() == NULL,
897 "the result should be NULL if the VM op did not succeed");
898 }
899
900 // Give a warning if we seem to be looping forever.
901 if ((QueuedAllocationWarningCount > 0) &&
902 (try_count % QueuedAllocationWarningCount == 0)) {
903 warning("G1CollectedHeap::mem_allocate retries %d times", try_count);
904 }
905 }
906
907 ShouldNotReachHere();
908 return NULL;
909 }
910
911 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size,
912 unsigned int *gc_count_before_ret) {
913 // Make sure you read the note in attempt_allocation_humongous().
914
915 assert_heap_not_locked_and_not_at_safepoint();
916 assert(!isHumongous(word_size), "attempt_allocation_slow() should not "
917 "be called for humongous allocation requests");
918
919 // We should only get here after the first-level allocation attempt
920 // (attempt_allocation()) failed to allocate.
921
922 // We will loop until a) we manage to successfully perform the
923 // allocation or b) we successfully schedule a collection which
924 // fails to perform the allocation. b) is the only case when we'll
925 // return NULL.
926 HeapWord* result = NULL;
927 for (int try_count = 1; /* we'll return */; try_count += 1) {
928 bool should_try_gc;
929 unsigned int gc_count_before;
930
931 {
932 MutexLockerEx x(Heap_lock);
933
934 result = _mutator_alloc_region.attempt_allocation_locked(word_size,
935 false /* bot_updates */);
936 if (result != NULL) {
937 return result;
938 }
939
940 // If we reach here, attempt_allocation_locked() above failed to
941 // allocate a new region. So the mutator alloc region should be NULL.
942 assert(_mutator_alloc_region.get() == NULL, "only way to get here");
943
944 if (GC_locker::is_active_and_needs_gc()) {
945 if (g1_policy()->can_expand_young_list()) {
946 // No need for an ergo verbose message here,
947 // can_expand_young_list() does this when it returns true.
948 result = _mutator_alloc_region.attempt_allocation_force(word_size,
949 false /* bot_updates */);
950 if (result != NULL) {
951 return result;
952 }
953 }
954 should_try_gc = false;
955 } else {
956 // The GCLocker may not be active but the GCLocker initiated
957 // GC may not yet have been performed (GCLocker::needs_gc()
958 // returns true). In this case we do not try this GC and
959 // wait until the GCLocker initiated GC is performed, and
960 // then retry the allocation.
961 if (GC_locker::needs_gc()) {
962 should_try_gc = false;
963 } else {
964 // Read the GC count while still holding the Heap_lock.
965 gc_count_before = total_collections();
966 should_try_gc = true;
967 }
968 }
969 }
970
971 if (should_try_gc) {
972 bool succeeded;
973 result = do_collection_pause(word_size, gc_count_before, &succeeded);
974 if (result != NULL) {
975 assert(succeeded, "only way to get back a non-NULL result");
976 return result;
977 }
978
979 if (succeeded) {
980 // If we get here we successfully scheduled a collection which
981 // failed to allocate. No point in trying to allocate
982 // further. We'll just return NULL.
983 MutexLockerEx x(Heap_lock);
984 *gc_count_before_ret = total_collections();
985 return NULL;
986 }
987 } else {
988 // The GCLocker is either active or the GCLocker initiated
989 // GC has not yet been performed. Stall until it is and
990 // then retry the allocation.
991 GC_locker::stall_until_clear();
992 }
993
994 // We can reach here if we were unsuccessul in scheduling a
995 // collection (because another thread beat us to it) or if we were
996 // stalled due to the GC locker. In either can we should retry the
997 // allocation attempt in case another thread successfully
998 // performed a collection and reclaimed enough space. We do the
999 // first attempt (without holding the Heap_lock) here and the
1000 // follow-on attempt will be at the start of the next loop
1001 // iteration (after taking the Heap_lock).
1002 result = _mutator_alloc_region.attempt_allocation(word_size,
1003 false /* bot_updates */);
1004 if (result != NULL) {
1005 return result;
1006 }
1007
1008 // Give a warning if we seem to be looping forever.
1009 if ((QueuedAllocationWarningCount > 0) &&
1010 (try_count % QueuedAllocationWarningCount == 0)) {
1011 warning("G1CollectedHeap::attempt_allocation_slow() "
1012 "retries %d times", try_count);
1013 }
1014 }
1015
1016 ShouldNotReachHere();
1017 return NULL;
1018 }
1019
1020 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size,
1021 unsigned int * gc_count_before_ret) {
1022 // The structure of this method has a lot of similarities to
1023 // attempt_allocation_slow(). The reason these two were not merged
1024 // into a single one is that such a method would require several "if
1025 // allocation is not humongous do this, otherwise do that"
1026 // conditional paths which would obscure its flow. In fact, an early
1027 // version of this code did use a unified method which was harder to
1028 // follow and, as a result, it had subtle bugs that were hard to
1029 // track down. So keeping these two methods separate allows each to
1030 // be more readable. It will be good to keep these two in sync as
1031 // much as possible.
1032
1033 assert_heap_not_locked_and_not_at_safepoint();
1034 assert(isHumongous(word_size), "attempt_allocation_humongous() "
1035 "should only be called for humongous allocations");
1036
1037 // Humongous objects can exhaust the heap quickly, so we should check if we
1038 // need to start a marking cycle at each humongous object allocation. We do
1039 // the check before we do the actual allocation. The reason for doing it
1040 // before the allocation is that we avoid having to keep track of the newly
1041 // allocated memory while we do a GC.
1042 if (g1_policy()->need_to_start_conc_mark("concurrent humongous allocation",
1043 word_size)) {
1044 collect(GCCause::_g1_humongous_allocation);
1045 }
1046
1047 // We will loop until a) we manage to successfully perform the
1048 // allocation or b) we successfully schedule a collection which
1049 // fails to perform the allocation. b) is the only case when we'll
1050 // return NULL.
1051 HeapWord* result = NULL;
1052 for (int try_count = 1; /* we'll return */; try_count += 1) {
1053 bool should_try_gc;
1054 unsigned int gc_count_before;
1055
1056 {
1057 MutexLockerEx x(Heap_lock);
1058
1059 // Given that humongous objects are not allocated in young
1060 // regions, we'll first try to do the allocation without doing a
1061 // collection hoping that there's enough space in the heap.
1062 result = humongous_obj_allocate(word_size);
1063 if (result != NULL) {
1064 return result;
1065 }
1066
1067 if (GC_locker::is_active_and_needs_gc()) {
1068 should_try_gc = false;
1069 } else {
1070 // The GCLocker may not be active but the GCLocker initiated
1071 // GC may not yet have been performed (GCLocker::needs_gc()
1072 // returns true). In this case we do not try this GC and
1073 // wait until the GCLocker initiated GC is performed, and
1074 // then retry the allocation.
1075 if (GC_locker::needs_gc()) {
1076 should_try_gc = false;
1077 } else {
1078 // Read the GC count while still holding the Heap_lock.
1079 gc_count_before = total_collections();
1080 should_try_gc = true;
1081 }
1082 }
1083 }
1084
1085 if (should_try_gc) {
1086 // If we failed to allocate the humongous object, we should try to
1087 // do a collection pause (if we're allowed) in case it reclaims
1088 // enough space for the allocation to succeed after the pause.
1089
1090 bool succeeded;
1091 result = do_collection_pause(word_size, gc_count_before, &succeeded);
1092 if (result != NULL) {
1093 assert(succeeded, "only way to get back a non-NULL result");
1094 return result;
1095 }
1096
1097 if (succeeded) {
1098 // If we get here we successfully scheduled a collection which
1099 // failed to allocate. No point in trying to allocate
1100 // further. We'll just return NULL.
1101 MutexLockerEx x(Heap_lock);
1102 *gc_count_before_ret = total_collections();
1103 return NULL;
1104 }
1105 } else {
1106 // The GCLocker is either active or the GCLocker initiated
1107 // GC has not yet been performed. Stall until it is and
1108 // then retry the allocation.
1109 GC_locker::stall_until_clear();
1110 }
1111
1112 // We can reach here if we were unsuccessul in scheduling a
1113 // collection (because another thread beat us to it) or if we were
1114 // stalled due to the GC locker. In either can we should retry the
1115 // allocation attempt in case another thread successfully
1116 // performed a collection and reclaimed enough space. Give a
1117 // warning if we seem to be looping forever.
1118
1119 if ((QueuedAllocationWarningCount > 0) &&
1120 (try_count % QueuedAllocationWarningCount == 0)) {
1121 warning("G1CollectedHeap::attempt_allocation_humongous() "
1122 "retries %d times", try_count);
1123 }
1124 }
1125
1126 ShouldNotReachHere();
1127 return NULL;
1128 }
1129
1130 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size,
1131 bool expect_null_mutator_alloc_region) {
1132 assert_at_safepoint(true /* should_be_vm_thread */);
1133 assert(_mutator_alloc_region.get() == NULL ||
1134 !expect_null_mutator_alloc_region,
1135 "the current alloc region was unexpectedly found to be non-NULL");
1136
1137 if (!isHumongous(word_size)) {
1138 return _mutator_alloc_region.attempt_allocation_locked(word_size,
1139 false /* bot_updates */);
1140 } else {
1141 HeapWord* result = humongous_obj_allocate(word_size);
1142 if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) {
1143 g1_policy()->set_initiate_conc_mark_if_possible();
1144 }
1145 return result;
1146 }
1147
1148 ShouldNotReachHere();
1149 }
1150
1151 class PostMCRemSetClearClosure: public HeapRegionClosure {
1152 ModRefBarrierSet* _mr_bs;
1153 public:
1154 PostMCRemSetClearClosure(ModRefBarrierSet* mr_bs) : _mr_bs(mr_bs) {}
1155 bool doHeapRegion(HeapRegion* r) {
1156 r->reset_gc_time_stamp();
1157 if (r->continuesHumongous())
1158 return false;
1159 HeapRegionRemSet* hrrs = r->rem_set();
1160 if (hrrs != NULL) hrrs->clear();
1161 // You might think here that we could clear just the cards
1162 // corresponding to the used region. But no: if we leave a dirty card
1163 // in a region we might allocate into, then it would prevent that card
1164 // from being enqueued, and cause it to be missed.
1165 // Re: the performance cost: we shouldn't be doing full GC anyway!
1166 _mr_bs->clear(MemRegion(r->bottom(), r->end()));
1167 return false;
1168 }
1169 };
1170
1171
1172 class PostMCRemSetInvalidateClosure: public HeapRegionClosure {
1173 ModRefBarrierSet* _mr_bs;
1174 public:
1175 PostMCRemSetInvalidateClosure(ModRefBarrierSet* mr_bs) : _mr_bs(mr_bs) {}
1176 bool doHeapRegion(HeapRegion* r) {
1177 if (r->continuesHumongous()) return false;
1178 if (r->used_region().word_size() != 0) {
1179 _mr_bs->invalidate(r->used_region(), true /*whole heap*/);
1180 }
1181 return false;
1182 }
1183 };
1184
1185 class RebuildRSOutOfRegionClosure: public HeapRegionClosure {
1186 G1CollectedHeap* _g1h;
1187 UpdateRSOopClosure _cl;
1188 int _worker_i;
1189 public:
1190 RebuildRSOutOfRegionClosure(G1CollectedHeap* g1, int worker_i = 0) :
1191 _cl(g1->g1_rem_set(), worker_i),
1192 _worker_i(worker_i),
1193 _g1h(g1)
1194 { }
1195
1196 bool doHeapRegion(HeapRegion* r) {
1197 if (!r->continuesHumongous()) {
1198 _cl.set_from(r);
1199 r->oop_iterate(&_cl);
1200 }
1201 return false;
1202 }
1203 };
1204
1205 class ParRebuildRSTask: public AbstractGangTask {
1206 G1CollectedHeap* _g1;
1207 public:
1208 ParRebuildRSTask(G1CollectedHeap* g1)
1209 : AbstractGangTask("ParRebuildRSTask"),
1210 _g1(g1)
1211 { }
1212
1213 void work(uint worker_id) {
1214 RebuildRSOutOfRegionClosure rebuild_rs(_g1, worker_id);
1215 _g1->heap_region_par_iterate_chunked(&rebuild_rs, worker_id,
1216 _g1->workers()->active_workers(),
1217 HeapRegion::RebuildRSClaimValue);
1218 }
1219 };
1220
1221 class PostCompactionPrinterClosure: public HeapRegionClosure {
1222 private:
1223 G1HRPrinter* _hr_printer;
1224 public:
1225 bool doHeapRegion(HeapRegion* hr) {
1226 assert(!hr->is_young(), "not expecting to find young regions");
1227 // We only generate output for non-empty regions.
1228 if (!hr->is_empty()) {
1229 if (!hr->isHumongous()) {
1230 _hr_printer->post_compaction(hr, G1HRPrinter::Old);
1231 } else if (hr->startsHumongous()) {
1232 if (hr->capacity() == HeapRegion::GrainBytes) {
1233 // single humongous region
1234 _hr_printer->post_compaction(hr, G1HRPrinter::SingleHumongous);
1235 } else {
1236 _hr_printer->post_compaction(hr, G1HRPrinter::StartsHumongous);
1237 }
1238 } else {
1239 assert(hr->continuesHumongous(), "only way to get here");
1240 _hr_printer->post_compaction(hr, G1HRPrinter::ContinuesHumongous);
1241 }
1242 }
1243 return false;
1244 }
1245
1246 PostCompactionPrinterClosure(G1HRPrinter* hr_printer)
1247 : _hr_printer(hr_printer) { }
1248 };
1249
1250 bool G1CollectedHeap::do_collection(bool explicit_gc,
1251 bool clear_all_soft_refs,
1252 size_t word_size) {
1253 assert_at_safepoint(true /* should_be_vm_thread */);
1254
1255 if (GC_locker::check_active_before_gc()) {
1256 return false;
1257 }
1258
1259 SvcGCMarker sgcm(SvcGCMarker::FULL);
1260 ResourceMark rm;
1261
1262 print_heap_before_gc();
1263
1264 HRSPhaseSetter x(HRSPhaseFullGC);
1265 verify_region_sets_optional();
1266
1267 const bool do_clear_all_soft_refs = clear_all_soft_refs ||
1268 collector_policy()->should_clear_all_soft_refs();
1269
1270 ClearedAllSoftRefs casr(do_clear_all_soft_refs, collector_policy());
1271
1272 {
1273 IsGCActiveMark x;
1274
1275 // Timing
1276 assert(gc_cause() != GCCause::_java_lang_system_gc || explicit_gc, "invariant");
1277 gclog_or_tty->date_stamp(G1Log::fine() && PrintGCDateStamps);
1278 TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty);
1279
1280 TraceTime t(GCCauseString("Full GC", gc_cause()), G1Log::fine(), true, gclog_or_tty);
1281 TraceCollectorStats tcs(g1mm()->full_collection_counters());
1282 TraceMemoryManagerStats tms(true /* fullGC */, gc_cause());
1283
1284 double start = os::elapsedTime();
1285 g1_policy()->record_full_collection_start();
1286
1287 // Note: When we have a more flexible GC logging framework that
1288 // allows us to add optional attributes to a GC log record we
1289 // could consider timing and reporting how long we wait in the
1290 // following two methods.
1291 wait_while_free_regions_coming();
1292 // If we start the compaction before the CM threads finish
1293 // scanning the root regions we might trip them over as we'll
1294 // be moving objects / updating references. So let's wait until
1295 // they are done. By telling them to abort, they should complete
1296 // early.
1297 _cm->root_regions()->abort();
1298 _cm->root_regions()->wait_until_scan_finished();
1299 append_secondary_free_list_if_not_empty_with_lock();
1300
1301 gc_prologue(true);
1302 increment_total_collections(true /* full gc */);
1303 increment_old_marking_cycles_started();
1304
1305 size_t g1h_prev_used = used();
1306 assert(used() == recalculate_used(), "Should be equal");
1307
1308 if (VerifyBeforeGC && total_collections() >= VerifyGCStartAt) {
1309 HandleMark hm; // Discard invalid handles created during verification
1310 gclog_or_tty->print(" VerifyBeforeGC:");
1311 prepare_for_verify();
1312 Universe::verify(/* silent */ false,
1313 /* option */ VerifyOption_G1UsePrevMarking);
1314
1315 }
1316 pre_full_gc_dump();
1317
1318 COMPILER2_PRESENT(DerivedPointerTable::clear());
1319
1320 // Disable discovery and empty the discovered lists
1321 // for the CM ref processor.
1322 ref_processor_cm()->disable_discovery();
1323 ref_processor_cm()->abandon_partial_discovery();
1324 ref_processor_cm()->verify_no_references_recorded();
1325
1326 // Abandon current iterations of concurrent marking and concurrent
1327 // refinement, if any are in progress. We have to do this before
1328 // wait_until_scan_finished() below.
1329 concurrent_mark()->abort();
1330
1331 // Make sure we'll choose a new allocation region afterwards.
1332 release_mutator_alloc_region();
1333 abandon_gc_alloc_regions();
1334 g1_rem_set()->cleanupHRRS();
1335
1336 // We should call this after we retire any currently active alloc
1337 // regions so that all the ALLOC / RETIRE events are generated
1338 // before the start GC event.
1339 _hr_printer.start_gc(true /* full */, (size_t) total_collections());
1340
1341 // We may have added regions to the current incremental collection
1342 // set between the last GC or pause and now. We need to clear the
1343 // incremental collection set and then start rebuilding it afresh
1344 // after this full GC.
1345 abandon_collection_set(g1_policy()->inc_cset_head());
1346 g1_policy()->clear_incremental_cset();
1347 g1_policy()->stop_incremental_cset_building();
1348
1349 tear_down_region_sets(false /* free_list_only */);
1350 g1_policy()->set_gcs_are_young(true);
1351
1352 // See the comments in g1CollectedHeap.hpp and
1353 // G1CollectedHeap::ref_processing_init() about
1354 // how reference processing currently works in G1.
1355
1356 // Temporarily make discovery by the STW ref processor single threaded (non-MT).
1357 ReferenceProcessorMTDiscoveryMutator stw_rp_disc_ser(ref_processor_stw(), false);
1358
1359 // Temporarily clear the STW ref processor's _is_alive_non_header field.
1360 ReferenceProcessorIsAliveMutator stw_rp_is_alive_null(ref_processor_stw(), NULL);
1361
1362 ref_processor_stw()->enable_discovery(true /*verify_disabled*/, true /*verify_no_refs*/);
1363 ref_processor_stw()->setup_policy(do_clear_all_soft_refs);
1364
1365 // Do collection work
1366 {
1367 HandleMark hm; // Discard invalid handles created during gc
1368 G1MarkSweep::invoke_at_safepoint(ref_processor_stw(), do_clear_all_soft_refs);
1369 }
1370
1371 assert(free_regions() == 0, "we should not have added any free regions");
1372 rebuild_region_sets(false /* free_list_only */);
1373
1374 // Enqueue any discovered reference objects that have
1375 // not been removed from the discovered lists.
1376 ref_processor_stw()->enqueue_discovered_references();
1377
1378 COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
1379
1380 MemoryService::track_memory_usage();
1381
1382 if (VerifyAfterGC && total_collections() >= VerifyGCStartAt) {
1383 HandleMark hm; // Discard invalid handles created during verification
1384 gclog_or_tty->print(" VerifyAfterGC:");
1385 prepare_for_verify();
1386 Universe::verify(/* silent */ false,
1387 /* option */ VerifyOption_G1UsePrevMarking);
1388
1389 }
1390
1391 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
1392 ref_processor_stw()->verify_no_references_recorded();
1393
1394 // Note: since we've just done a full GC, concurrent
1395 // marking is no longer active. Therefore we need not
1396 // re-enable reference discovery for the CM ref processor.
1397 // That will be done at the start of the next marking cycle.
1398 assert(!ref_processor_cm()->discovery_enabled(), "Postcondition");
1399 ref_processor_cm()->verify_no_references_recorded();
1400
1401 reset_gc_time_stamp();
1402 // Since everything potentially moved, we will clear all remembered
1403 // sets, and clear all cards. Later we will rebuild remebered
1404 // sets. We will also reset the GC time stamps of the regions.
1405 PostMCRemSetClearClosure rs_clear(mr_bs());
1406 heap_region_iterate(&rs_clear);
1407
1408 // Resize the heap if necessary.
1409 resize_if_necessary_after_full_collection(explicit_gc ? 0 : word_size);
1410
1411 if (_hr_printer.is_active()) {
1412 // We should do this after we potentially resize the heap so
1413 // that all the COMMIT / UNCOMMIT events are generated before
1414 // the end GC event.
1415
1416 PostCompactionPrinterClosure cl(hr_printer());
1417 heap_region_iterate(&cl);
1418
1419 _hr_printer.end_gc(true /* full */, (size_t) total_collections());
1420 }
1421
1422 if (_cg1r->use_cache()) {
1423 _cg1r->clear_and_record_card_counts();
1424 _cg1r->clear_hot_cache();
1425 }
1426
1427 // Rebuild remembered sets of all regions.
1428 if (G1CollectedHeap::use_parallel_gc_threads()) {
1429 uint n_workers =
1430 AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
1431 workers()->active_workers(),
1432 Threads::number_of_non_daemon_threads());
1433 assert(UseDynamicNumberOfGCThreads ||
1434 n_workers == workers()->total_workers(),
1435 "If not dynamic should be using all the workers");
1436 workers()->set_active_workers(n_workers);
1437 // Set parallel threads in the heap (_n_par_threads) only
1438 // before a parallel phase and always reset it to 0 after
1439 // the phase so that the number of parallel threads does
1440 // no get carried forward to a serial phase where there
1441 // may be code that is "possibly_parallel".
1442 set_par_threads(n_workers);
1443
1444 ParRebuildRSTask rebuild_rs_task(this);
1445 assert(check_heap_region_claim_values(
1446 HeapRegion::InitialClaimValue), "sanity check");
1447 assert(UseDynamicNumberOfGCThreads ||
1448 workers()->active_workers() == workers()->total_workers(),
1449 "Unless dynamic should use total workers");
1450 // Use the most recent number of active workers
1451 assert(workers()->active_workers() > 0,
1452 "Active workers not properly set");
1453 set_par_threads(workers()->active_workers());
1454 workers()->run_task(&rebuild_rs_task);
1455 set_par_threads(0);
1456 assert(check_heap_region_claim_values(
1457 HeapRegion::RebuildRSClaimValue), "sanity check");
1458 reset_heap_region_claim_values();
1459 } else {
1460 RebuildRSOutOfRegionClosure rebuild_rs(this);
1461 heap_region_iterate(&rebuild_rs);
1462 }
1463
1464 if (G1Log::fine()) {
1465 print_size_transition(gclog_or_tty, g1h_prev_used, used(), capacity());
1466 }
1467
1468 if (true) { // FIXME
1469 // Ask the permanent generation to adjust size for full collections
1470 perm()->compute_new_size();
1471 }
1472
1473 // Start a new incremental collection set for the next pause
1474 assert(g1_policy()->collection_set() == NULL, "must be");
1475 g1_policy()->start_incremental_cset_building();
1476
1477 // Clear the _cset_fast_test bitmap in anticipation of adding
1478 // regions to the incremental collection set for the next
1479 // evacuation pause.
1480 clear_cset_fast_test();
1481
1482 init_mutator_alloc_region();
1483
1484 double end = os::elapsedTime();
1485 g1_policy()->record_full_collection_end();
1486
1487 #ifdef TRACESPINNING
1488 ParallelTaskTerminator::print_termination_counts();
1489 #endif
1490
1491 gc_epilogue(true);
1492
1493 // Discard all rset updates
1494 JavaThread::dirty_card_queue_set().abandon_logs();
1495 assert(!G1DeferredRSUpdate
1496 || (G1DeferredRSUpdate && (dirty_card_queue_set().completed_buffers_num() == 0)), "Should not be any");
1497
1498 _young_list->reset_sampled_info();
1499 // At this point there should be no regions in the
1500 // entire heap tagged as young.
1501 assert( check_young_list_empty(true /* check_heap */),
1502 "young list should be empty at this point");
1503
1504 // Update the number of full collections that have been completed.
1505 increment_old_marking_cycles_completed(false /* concurrent */);
1506
1507 _hrs.verify_optional();
1508 verify_region_sets_optional();
1509
1510 print_heap_after_gc();
1511
1512 // We must call G1MonitoringSupport::update_sizes() in the same scoping level
1513 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
1514 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
1515 // before any GC notifications are raised.
1516 g1mm()->update_sizes();
1517 }
1518
1519 post_full_gc_dump();
1520
1521 return true;
1522 }
1523
1524 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) {
1525 // do_collection() will return whether it succeeded in performing
1526 // the GC. Currently, there is no facility on the
1527 // do_full_collection() API to notify the caller than the collection
1528 // did not succeed (e.g., because it was locked out by the GC
1529 // locker). So, right now, we'll ignore the return value.
1530 bool dummy = do_collection(true, /* explicit_gc */
1531 clear_all_soft_refs,
1532 0 /* word_size */);
1533 }
1534
1535 // This code is mostly copied from TenuredGeneration.
1536 void
1537 G1CollectedHeap::
1538 resize_if_necessary_after_full_collection(size_t word_size) {
1539 assert(MinHeapFreeRatio <= MaxHeapFreeRatio, "sanity check");
1540
1541 // Include the current allocation, if any, and bytes that will be
1542 // pre-allocated to support collections, as "used".
1543 const size_t used_after_gc = used();
1544 const size_t capacity_after_gc = capacity();
1545 const size_t free_after_gc = capacity_after_gc - used_after_gc;
1546
1547 // This is enforced in arguments.cpp.
1548 assert(MinHeapFreeRatio <= MaxHeapFreeRatio,
1549 "otherwise the code below doesn't make sense");
1550
1551 // We don't have floating point command-line arguments
1552 const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0;
1553 const double maximum_used_percentage = 1.0 - minimum_free_percentage;
1554 const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0;
1555 const double minimum_used_percentage = 1.0 - maximum_free_percentage;
1556
1557 const size_t min_heap_size = collector_policy()->min_heap_byte_size();
1558 const size_t max_heap_size = collector_policy()->max_heap_byte_size();
1559
1560 // We have to be careful here as these two calculations can overflow
1561 // 32-bit size_t's.
1562 double used_after_gc_d = (double) used_after_gc;
1563 double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage;
1564 double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage;
1565
1566 // Let's make sure that they are both under the max heap size, which
1567 // by default will make them fit into a size_t.
1568 double desired_capacity_upper_bound = (double) max_heap_size;
1569 minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d,
1570 desired_capacity_upper_bound);
1571 maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d,
1572 desired_capacity_upper_bound);
1573
1574 // We can now safely turn them into size_t's.
1575 size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d;
1576 size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d;
1577
1578 // This assert only makes sense here, before we adjust them
1579 // with respect to the min and max heap size.
1580 assert(minimum_desired_capacity <= maximum_desired_capacity,
1581 err_msg("minimum_desired_capacity = "SIZE_FORMAT", "
1582 "maximum_desired_capacity = "SIZE_FORMAT,
1583 minimum_desired_capacity, maximum_desired_capacity));
1584
1585 // Should not be greater than the heap max size. No need to adjust
1586 // it with respect to the heap min size as it's a lower bound (i.e.,
1587 // we'll try to make the capacity larger than it, not smaller).
1588 minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size);
1589 // Should not be less than the heap min size. No need to adjust it
1590 // with respect to the heap max size as it's an upper bound (i.e.,
1591 // we'll try to make the capacity smaller than it, not greater).
1592 maximum_desired_capacity = MAX2(maximum_desired_capacity, min_heap_size);
1593
1594 if (capacity_after_gc < minimum_desired_capacity) {
1595 // Don't expand unless it's significant
1596 size_t expand_bytes = minimum_desired_capacity - capacity_after_gc;
1597 ergo_verbose4(ErgoHeapSizing,
1598 "attempt heap expansion",
1599 ergo_format_reason("capacity lower than "
1600 "min desired capacity after Full GC")
1601 ergo_format_byte("capacity")
1602 ergo_format_byte("occupancy")
1603 ergo_format_byte_perc("min desired capacity"),
1604 capacity_after_gc, used_after_gc,
1605 minimum_desired_capacity, (double) MinHeapFreeRatio);
1606 expand(expand_bytes);
1607
1608 // No expansion, now see if we want to shrink
1609 } else if (capacity_after_gc > maximum_desired_capacity) {
1610 // Capacity too large, compute shrinking size
1611 size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity;
1612 ergo_verbose4(ErgoHeapSizing,
1613 "attempt heap shrinking",
1614 ergo_format_reason("capacity higher than "
1615 "max desired capacity after Full GC")
1616 ergo_format_byte("capacity")
1617 ergo_format_byte("occupancy")
1618 ergo_format_byte_perc("max desired capacity"),
1619 capacity_after_gc, used_after_gc,
1620 maximum_desired_capacity, (double) MaxHeapFreeRatio);
1621 shrink(shrink_bytes);
1622 }
1623 }
1624
1625
1626 HeapWord*
1627 G1CollectedHeap::satisfy_failed_allocation(size_t word_size,
1628 bool* succeeded) {
1629 assert_at_safepoint(true /* should_be_vm_thread */);
1630
1631 *succeeded = true;
1632 // Let's attempt the allocation first.
1633 HeapWord* result =
1634 attempt_allocation_at_safepoint(word_size,
1635 false /* expect_null_mutator_alloc_region */);
1636 if (result != NULL) {
1637 assert(*succeeded, "sanity");
1638 return result;
1639 }
1640
1641 // In a G1 heap, we're supposed to keep allocation from failing by
1642 // incremental pauses. Therefore, at least for now, we'll favor
1643 // expansion over collection. (This might change in the future if we can
1644 // do something smarter than full collection to satisfy a failed alloc.)
1645 result = expand_and_allocate(word_size);
1646 if (result != NULL) {
1647 assert(*succeeded, "sanity");
1648 return result;
1649 }
1650
1651 // Expansion didn't work, we'll try to do a Full GC.
1652 bool gc_succeeded = do_collection(false, /* explicit_gc */
1653 false, /* clear_all_soft_refs */
1654 word_size);
1655 if (!gc_succeeded) {
1656 *succeeded = false;
1657 return NULL;
1658 }
1659
1660 // Retry the allocation
1661 result = attempt_allocation_at_safepoint(word_size,
1662 true /* expect_null_mutator_alloc_region */);
1663 if (result != NULL) {
1664 assert(*succeeded, "sanity");
1665 return result;
1666 }
1667
1668 // Then, try a Full GC that will collect all soft references.
1669 gc_succeeded = do_collection(false, /* explicit_gc */
1670 true, /* clear_all_soft_refs */
1671 word_size);
1672 if (!gc_succeeded) {
1673 *succeeded = false;
1674 return NULL;
1675 }
1676
1677 // Retry the allocation once more
1678 result = attempt_allocation_at_safepoint(word_size,
1679 true /* expect_null_mutator_alloc_region */);
1680 if (result != NULL) {
1681 assert(*succeeded, "sanity");
1682 return result;
1683 }
1684
1685 assert(!collector_policy()->should_clear_all_soft_refs(),
1686 "Flag should have been handled and cleared prior to this point");
1687
1688 // What else? We might try synchronous finalization later. If the total
1689 // space available is large enough for the allocation, then a more
1690 // complete compaction phase than we've tried so far might be
1691 // appropriate.
1692 assert(*succeeded, "sanity");
1693 return NULL;
1694 }
1695
1696 // Attempting to expand the heap sufficiently
1697 // to support an allocation of the given "word_size". If
1698 // successful, perform the allocation and return the address of the
1699 // allocated block, or else "NULL".
1700
1701 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size) {
1702 assert_at_safepoint(true /* should_be_vm_thread */);
1703
1704 verify_region_sets_optional();
1705
1706 size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes);
1707 ergo_verbose1(ErgoHeapSizing,
1708 "attempt heap expansion",
1709 ergo_format_reason("allocation request failed")
1710 ergo_format_byte("allocation request"),
1711 word_size * HeapWordSize);
1712 if (expand(expand_bytes)) {
1713 _hrs.verify_optional();
1714 verify_region_sets_optional();
1715 return attempt_allocation_at_safepoint(word_size,
1716 false /* expect_null_mutator_alloc_region */);
1717 }
1718 return NULL;
1719 }
1720
1721 void G1CollectedHeap::update_committed_space(HeapWord* old_end,
1722 HeapWord* new_end) {
1723 assert(old_end != new_end, "don't call this otherwise");
1724 assert((HeapWord*) _g1_storage.high() == new_end, "invariant");
1725
1726 // Update the committed mem region.
1727 _g1_committed.set_end(new_end);
1728 // Tell the card table about the update.
1729 Universe::heap()->barrier_set()->resize_covered_region(_g1_committed);
1730 // Tell the BOT about the update.
1731 _bot_shared->resize(_g1_committed.word_size());
1732 }
1733
1734 bool G1CollectedHeap::expand(size_t expand_bytes) {
1735 size_t old_mem_size = _g1_storage.committed_size();
1736 size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes);
1737 aligned_expand_bytes = align_size_up(aligned_expand_bytes,
1738 HeapRegion::GrainBytes);
1739 ergo_verbose2(ErgoHeapSizing,
1740 "expand the heap",
1741 ergo_format_byte("requested expansion amount")
1742 ergo_format_byte("attempted expansion amount"),
1743 expand_bytes, aligned_expand_bytes);
1744
1745 // First commit the memory.
1746 HeapWord* old_end = (HeapWord*) _g1_storage.high();
1747 bool successful = _g1_storage.expand_by(aligned_expand_bytes);
1748 if (successful) {
1749 // Then propagate this update to the necessary data structures.
1750 HeapWord* new_end = (HeapWord*) _g1_storage.high();
1751 update_committed_space(old_end, new_end);
1752
1753 FreeRegionList expansion_list("Local Expansion List");
1754 MemRegion mr = _hrs.expand_by(old_end, new_end, &expansion_list);
1755 assert(mr.start() == old_end, "post-condition");
1756 // mr might be a smaller region than what was requested if
1757 // expand_by() was unable to allocate the HeapRegion instances
1758 assert(mr.end() <= new_end, "post-condition");
1759
1760 size_t actual_expand_bytes = mr.byte_size();
1761 assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition");
1762 assert(actual_expand_bytes == expansion_list.total_capacity_bytes(),
1763 "post-condition");
1764 if (actual_expand_bytes < aligned_expand_bytes) {
1765 // We could not expand _hrs to the desired size. In this case we
1766 // need to shrink the committed space accordingly.
1767 assert(mr.end() < new_end, "invariant");
1768
1769 size_t diff_bytes = aligned_expand_bytes - actual_expand_bytes;
1770 // First uncommit the memory.
1771 _g1_storage.shrink_by(diff_bytes);
1772 // Then propagate this update to the necessary data structures.
1773 update_committed_space(new_end, mr.end());
1774 }
1775 _free_list.add_as_tail(&expansion_list);
1776
1777 if (_hr_printer.is_active()) {
1778 HeapWord* curr = mr.start();
1779 while (curr < mr.end()) {
1780 HeapWord* curr_end = curr + HeapRegion::GrainWords;
1781 _hr_printer.commit(curr, curr_end);
1782 curr = curr_end;
1783 }
1784 assert(curr == mr.end(), "post-condition");
1785 }
1786 g1_policy()->record_new_heap_size(n_regions());
1787 } else {
1788 ergo_verbose0(ErgoHeapSizing,
1789 "did not expand the heap",
1790 ergo_format_reason("heap expansion operation failed"));
1791 // The expansion of the virtual storage space was unsuccessful.
1792 // Let's see if it was because we ran out of swap.
1793 if (G1ExitOnExpansionFailure &&
1794 _g1_storage.uncommitted_size() >= aligned_expand_bytes) {
1795 // We had head room...
1796 vm_exit_out_of_memory(aligned_expand_bytes, "G1 heap expansion");
1797 }
1798 }
1799 return successful;
1800 }
1801
1802 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) {
1803 size_t old_mem_size = _g1_storage.committed_size();
1804 size_t aligned_shrink_bytes =
1805 ReservedSpace::page_align_size_down(shrink_bytes);
1806 aligned_shrink_bytes = align_size_down(aligned_shrink_bytes,
1807 HeapRegion::GrainBytes);
1808 uint num_regions_deleted = 0;
1809 MemRegion mr = _hrs.shrink_by(aligned_shrink_bytes, &num_regions_deleted);
1810 HeapWord* old_end = (HeapWord*) _g1_storage.high();
1811 assert(mr.end() == old_end, "post-condition");
1812
1813 ergo_verbose3(ErgoHeapSizing,
1814 "shrink the heap",
1815 ergo_format_byte("requested shrinking amount")
1816 ergo_format_byte("aligned shrinking amount")
1817 ergo_format_byte("attempted shrinking amount"),
1818 shrink_bytes, aligned_shrink_bytes, mr.byte_size());
1819 if (mr.byte_size() > 0) {
1820 if (_hr_printer.is_active()) {
1821 HeapWord* curr = mr.end();
1822 while (curr > mr.start()) {
1823 HeapWord* curr_end = curr;
1824 curr -= HeapRegion::GrainWords;
1825 _hr_printer.uncommit(curr, curr_end);
1826 }
1827 assert(curr == mr.start(), "post-condition");
1828 }
1829
1830 _g1_storage.shrink_by(mr.byte_size());
1831 HeapWord* new_end = (HeapWord*) _g1_storage.high();
1832 assert(mr.start() == new_end, "post-condition");
1833
1834 _expansion_regions += num_regions_deleted;
1835 update_committed_space(old_end, new_end);
1836 HeapRegionRemSet::shrink_heap(n_regions());
1837 g1_policy()->record_new_heap_size(n_regions());
1838 } else {
1839 ergo_verbose0(ErgoHeapSizing,
1840 "did not shrink the heap",
1841 ergo_format_reason("heap shrinking operation failed"));
1842 }
1843 }
1844
1845 void G1CollectedHeap::shrink(size_t shrink_bytes) {
1846 verify_region_sets_optional();
1847
1848 // We should only reach here at the end of a Full GC which means we
1849 // should not not be holding to any GC alloc regions. The method
1850 // below will make sure of that and do any remaining clean up.
1851 abandon_gc_alloc_regions();
1852
1853 // Instead of tearing down / rebuilding the free lists here, we
1854 // could instead use the remove_all_pending() method on free_list to
1855 // remove only the ones that we need to remove.
1856 tear_down_region_sets(true /* free_list_only */);
1857 shrink_helper(shrink_bytes);
1858 rebuild_region_sets(true /* free_list_only */);
1859
1860 _hrs.verify_optional();
1861 verify_region_sets_optional();
1862 }
1863
1864 // Public methods.
1865
1866 #ifdef _MSC_VER // the use of 'this' below gets a warning, make it go away
1867 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list
1868 #endif // _MSC_VER
1869
1870
1871 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* policy_) :
1872 SharedHeap(policy_),
1873 _g1_policy(policy_),
1874 _dirty_card_queue_set(false),
1875 _into_cset_dirty_card_queue_set(false),
1876 _is_alive_closure_cm(this),
1877 _is_alive_closure_stw(this),
1878 _ref_processor_cm(NULL),
1879 _ref_processor_stw(NULL),
1880 _process_strong_tasks(new SubTasksDone(G1H_PS_NumElements)),
1881 _bot_shared(NULL),
1882 _objs_with_preserved_marks(NULL), _preserved_marks_of_objs(NULL),
1883 _evac_failure_scan_stack(NULL) ,
1884 _mark_in_progress(false),
1885 _cg1r(NULL), _summary_bytes_used(0),
1886 _g1mm(NULL),
1887 _refine_cte_cl(NULL),
1888 _full_collection(false),
1889 _free_list("Master Free List"),
1890 _secondary_free_list("Secondary Free List"),
1891 _old_set("Old Set"),
1892 _humongous_set("Master Humongous Set"),
1893 _free_regions_coming(false),
1894 _young_list(new YoungList(this)),
1895 _gc_time_stamp(0),
1896 _retained_old_gc_alloc_region(NULL),
1897 _expand_heap_after_alloc_failure(true),
1898 _surviving_young_words(NULL),
1899 _old_marking_cycles_started(0),
1900 _old_marking_cycles_completed(0),
1901 _in_cset_fast_test(NULL),
1902 _in_cset_fast_test_base(NULL),
1903 _dirty_cards_region_list(NULL),
1904 _worker_cset_start_region(NULL),
1905 _worker_cset_start_region_time_stamp(NULL) {
1906 _g1h = this; // To catch bugs.
1907 if (_process_strong_tasks == NULL || !_process_strong_tasks->valid()) {
1908 vm_exit_during_initialization("Failed necessary allocation.");
1909 }
1910
1911 _humongous_object_threshold_in_words = HeapRegion::GrainWords / 2;
1912
1913 int n_queues = MAX2((int)ParallelGCThreads, 1);
1914 _task_queues = new RefToScanQueueSet(n_queues);
1915
1916 int n_rem_sets = HeapRegionRemSet::num_par_rem_sets();
1917 assert(n_rem_sets > 0, "Invariant.");
1918
1919 HeapRegionRemSetIterator** iter_arr =
1920 NEW_C_HEAP_ARRAY(HeapRegionRemSetIterator*, n_queues, mtGC);
1921 for (int i = 0; i < n_queues; i++) {
1922 iter_arr[i] = new HeapRegionRemSetIterator();
1923 }
1924 _rem_set_iterator = iter_arr;
1925
1926 _worker_cset_start_region = NEW_C_HEAP_ARRAY(HeapRegion*, n_queues, mtGC);
1927 _worker_cset_start_region_time_stamp = NEW_C_HEAP_ARRAY(unsigned int, n_queues, mtGC);
1928
1929 for (int i = 0; i < n_queues; i++) {
1930 RefToScanQueue* q = new RefToScanQueue();
1931 q->initialize();
1932 _task_queues->register_queue(i, q);
1933 }
1934
1935 clear_cset_start_regions();
1936
1937 guarantee(_task_queues != NULL, "task_queues allocation failure.");
1938 }
1939
1940 jint G1CollectedHeap::initialize() {
1941 CollectedHeap::pre_initialize();
1942 os::enable_vtime();
1943
1944 G1Log::init();
1945
1946 // Necessary to satisfy locking discipline assertions.
1947
1948 MutexLocker x(Heap_lock);
1949
1950 // We have to initialize the printer before committing the heap, as
1951 // it will be used then.
1952 _hr_printer.set_active(G1PrintHeapRegions);
1953
1954 // While there are no constraints in the GC code that HeapWordSize
1955 // be any particular value, there are multiple other areas in the
1956 // system which believe this to be true (e.g. oop->object_size in some
1957 // cases incorrectly returns the size in wordSize units rather than
1958 // HeapWordSize).
1959 guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize");
1960
1961 size_t init_byte_size = collector_policy()->initial_heap_byte_size();
1962 size_t max_byte_size = collector_policy()->max_heap_byte_size();
1963
1964 // Ensure that the sizes are properly aligned.
1965 Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap");
1966 Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap");
1967
1968 _cg1r = new ConcurrentG1Refine();
1969
1970 // Reserve the maximum.
1971 PermanentGenerationSpec* pgs = collector_policy()->permanent_generation();
1972 // Includes the perm-gen.
1973
1974 // When compressed oops are enabled, the preferred heap base
1975 // is calculated by subtracting the requested size from the
1976 // 32Gb boundary and using the result as the base address for
1977 // heap reservation. If the requested size is not aligned to
1978 // HeapRegion::GrainBytes (i.e. the alignment that is passed
1979 // into the ReservedHeapSpace constructor) then the actual
1980 // base of the reserved heap may end up differing from the
1981 // address that was requested (i.e. the preferred heap base).
1982 // If this happens then we could end up using a non-optimal
1983 // compressed oops mode.
1984
1985 // Since max_byte_size is aligned to the size of a heap region (checked
1986 // above), we also need to align the perm gen size as it might not be.
1987 const size_t total_reserved = max_byte_size +
1988 align_size_up(pgs->max_size(), HeapRegion::GrainBytes);
1989 Universe::check_alignment(total_reserved, HeapRegion::GrainBytes, "g1 heap and perm");
1990
1991 char* addr = Universe::preferred_heap_base(total_reserved, Universe::UnscaledNarrowOop);
1992
1993 ReservedHeapSpace heap_rs(total_reserved, HeapRegion::GrainBytes,
1994 UseLargePages, addr);
1995
1996 if (UseCompressedOops) {
1997 if (addr != NULL && !heap_rs.is_reserved()) {
1998 // Failed to reserve at specified address - the requested memory
1999 // region is taken already, for example, by 'java' launcher.
2000 // Try again to reserver heap higher.
2001 addr = Universe::preferred_heap_base(total_reserved, Universe::ZeroBasedNarrowOop);
2002
2003 ReservedHeapSpace heap_rs0(total_reserved, HeapRegion::GrainBytes,
2004 UseLargePages, addr);
2005
2006 if (addr != NULL && !heap_rs0.is_reserved()) {
2007 // Failed to reserve at specified address again - give up.
2008 addr = Universe::preferred_heap_base(total_reserved, Universe::HeapBasedNarrowOop);
2009 assert(addr == NULL, "");
2010
2011 ReservedHeapSpace heap_rs1(total_reserved, HeapRegion::GrainBytes,
2012 UseLargePages, addr);
2013 heap_rs = heap_rs1;
2014 } else {
2015 heap_rs = heap_rs0;
2016 }
2017 }
2018 }
2019
2020 if (!heap_rs.is_reserved()) {
2021 vm_exit_during_initialization("Could not reserve enough space for object heap");
2022 return JNI_ENOMEM;
2023 }
2024
2025 // It is important to do this in a way such that concurrent readers can't
2026 // temporarily think somethings in the heap. (I've actually seen this
2027 // happen in asserts: DLD.)
2028 _reserved.set_word_size(0);
2029 _reserved.set_start((HeapWord*)heap_rs.base());
2030 _reserved.set_end((HeapWord*)(heap_rs.base() + heap_rs.size()));
2031
2032 _expansion_regions = (uint) (max_byte_size / HeapRegion::GrainBytes);
2033
2034 // Create the gen rem set (and barrier set) for the entire reserved region.
2035 _rem_set = collector_policy()->create_rem_set(_reserved, 2);
2036 set_barrier_set(rem_set()->bs());
2037 if (barrier_set()->is_a(BarrierSet::ModRef)) {
2038 _mr_bs = (ModRefBarrierSet*)_barrier_set;
2039 } else {
2040 vm_exit_during_initialization("G1 requires a mod ref bs.");
2041 return JNI_ENOMEM;
2042 }
2043
2044 // Also create a G1 rem set.
2045 if (mr_bs()->is_a(BarrierSet::CardTableModRef)) {
2046 _g1_rem_set = new G1RemSet(this, (CardTableModRefBS*)mr_bs());
2047 } else {
2048 vm_exit_during_initialization("G1 requires a cardtable mod ref bs.");
2049 return JNI_ENOMEM;
2050 }
2051
2052 // Carve out the G1 part of the heap.
2053
2054 ReservedSpace g1_rs = heap_rs.first_part(max_byte_size);
2055 _g1_reserved = MemRegion((HeapWord*)g1_rs.base(),
2056 g1_rs.size()/HeapWordSize);
2057 ReservedSpace perm_gen_rs = heap_rs.last_part(max_byte_size);
2058
2059 _perm_gen = pgs->init(perm_gen_rs, pgs->init_size(), rem_set());
2060
2061 _g1_storage.initialize(g1_rs, 0);
2062 _g1_committed = MemRegion((HeapWord*)_g1_storage.low(), (size_t) 0);
2063 _hrs.initialize((HeapWord*) _g1_reserved.start(),
2064 (HeapWord*) _g1_reserved.end(),
2065 _expansion_regions);
2066
2067 // 6843694 - ensure that the maximum region index can fit
2068 // in the remembered set structures.
2069 const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1;
2070 guarantee((max_regions() - 1) <= max_region_idx, "too many regions");
2071
2072 size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1;
2073 guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized");
2074 guarantee(HeapRegion::CardsPerRegion < max_cards_per_region,
2075 "too many cards per region");
2076
2077 HeapRegionSet::set_unrealistically_long_length(max_regions() + 1);
2078
2079 _bot_shared = new G1BlockOffsetSharedArray(_reserved,
2080 heap_word_size(init_byte_size));
2081
2082 _g1h = this;
2083
2084 _in_cset_fast_test_length = max_regions();
2085 _in_cset_fast_test_base =
2086 NEW_C_HEAP_ARRAY(bool, (size_t) _in_cset_fast_test_length, mtGC);
2087
2088 // We're biasing _in_cset_fast_test to avoid subtracting the
2089 // beginning of the heap every time we want to index; basically
2090 // it's the same with what we do with the card table.
2091 _in_cset_fast_test = _in_cset_fast_test_base -
2092 ((uintx) _g1_reserved.start() >> HeapRegion::LogOfHRGrainBytes);
2093
2094 // Clear the _cset_fast_test bitmap in anticipation of adding
2095 // regions to the incremental collection set for the first
2096 // evacuation pause.
2097 clear_cset_fast_test();
2098
2099 // Create the ConcurrentMark data structure and thread.
2100 // (Must do this late, so that "max_regions" is defined.)
2101 _cm = new ConcurrentMark(heap_rs, max_regions());
2102 _cmThread = _cm->cmThread();
2103
2104 // Initialize the from_card cache structure of HeapRegionRemSet.
2105 HeapRegionRemSet::init_heap(max_regions());
2106
2107 // Now expand into the initial heap size.
2108 if (!expand(init_byte_size)) {
2109 vm_exit_during_initialization("Failed to allocate initial heap.");
2110 return JNI_ENOMEM;
2111 }
2112
2113 // Perform any initialization actions delegated to the policy.
2114 g1_policy()->init();
2115
2116 _refine_cte_cl =
2117 new RefineCardTableEntryClosure(ConcurrentG1RefineThread::sts(),
2118 g1_rem_set(),
2119 concurrent_g1_refine());
2120 JavaThread::dirty_card_queue_set().set_closure(_refine_cte_cl);
2121
2122 JavaThread::satb_mark_queue_set().initialize(SATB_Q_CBL_mon,
2123 SATB_Q_FL_lock,
2124 G1SATBProcessCompletedThreshold,
2125 Shared_SATB_Q_lock);
2126
2127 JavaThread::dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon,
2128 DirtyCardQ_FL_lock,
2129 concurrent_g1_refine()->yellow_zone(),
2130 concurrent_g1_refine()->red_zone(),
2131 Shared_DirtyCardQ_lock);
2132
2133 if (G1DeferredRSUpdate) {
2134 dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon,
2135 DirtyCardQ_FL_lock,
2136 -1, // never trigger processing
2137 -1, // no limit on length
2138 Shared_DirtyCardQ_lock,
2139 &JavaThread::dirty_card_queue_set());
2140 }
2141
2142 // Initialize the card queue set used to hold cards containing
2143 // references into the collection set.
2144 _into_cset_dirty_card_queue_set.initialize(DirtyCardQ_CBL_mon,
2145 DirtyCardQ_FL_lock,
2146 -1, // never trigger processing
2147 -1, // no limit on length
2148 Shared_DirtyCardQ_lock,
2149 &JavaThread::dirty_card_queue_set());
2150
2151 // In case we're keeping closure specialization stats, initialize those
2152 // counts and that mechanism.
2153 SpecializationStats::clear();
2154
2155 // Do later initialization work for concurrent refinement.
2156 _cg1r->init();
2157
2158 // Here we allocate the dummy full region that is required by the
2159 // G1AllocRegion class. If we don't pass an address in the reserved
2160 // space here, lots of asserts fire.
2161
2162 HeapRegion* dummy_region = new_heap_region(0 /* index of bottom region */,
2163 _g1_reserved.start());
2164 // We'll re-use the same region whether the alloc region will
2165 // require BOT updates or not and, if it doesn't, then a non-young
2166 // region will complain that it cannot support allocations without
2167 // BOT updates. So we'll tag the dummy region as young to avoid that.
2168 dummy_region->set_young();
2169 // Make sure it's full.
2170 dummy_region->set_top(dummy_region->end());
2171 G1AllocRegion::setup(this, dummy_region);
2172
2173 init_mutator_alloc_region();
2174
2175 // Do create of the monitoring and management support so that
2176 // values in the heap have been properly initialized.
2177 _g1mm = new G1MonitoringSupport(this);
2178
2179 return JNI_OK;
2180 }
2181
2182 void G1CollectedHeap::ref_processing_init() {
2183 // Reference processing in G1 currently works as follows:
2184 //
2185 // * There are two reference processor instances. One is
2186 // used to record and process discovered references
2187 // during concurrent marking; the other is used to
2188 // record and process references during STW pauses
2189 // (both full and incremental).
2190 // * Both ref processors need to 'span' the entire heap as
2191 // the regions in the collection set may be dotted around.
2192 //
2193 // * For the concurrent marking ref processor:
2194 // * Reference discovery is enabled at initial marking.
2195 // * Reference discovery is disabled and the discovered
2196 // references processed etc during remarking.
2197 // * Reference discovery is MT (see below).
2198 // * Reference discovery requires a barrier (see below).
2199 // * Reference processing may or may not be MT
2200 // (depending on the value of ParallelRefProcEnabled
2201 // and ParallelGCThreads).
2202 // * A full GC disables reference discovery by the CM
2203 // ref processor and abandons any entries on it's
2204 // discovered lists.
2205 //
2206 // * For the STW processor:
2207 // * Non MT discovery is enabled at the start of a full GC.
2208 // * Processing and enqueueing during a full GC is non-MT.
2209 // * During a full GC, references are processed after marking.
2210 //
2211 // * Discovery (may or may not be MT) is enabled at the start
2212 // of an incremental evacuation pause.
2213 // * References are processed near the end of a STW evacuation pause.
2214 // * For both types of GC:
2215 // * Discovery is atomic - i.e. not concurrent.
2216 // * Reference discovery will not need a barrier.
2217
2218 SharedHeap::ref_processing_init();
2219 MemRegion mr = reserved_region();
2220
2221 // Concurrent Mark ref processor
2222 _ref_processor_cm =
2223 new ReferenceProcessor(mr, // span
2224 ParallelRefProcEnabled && (ParallelGCThreads > 1),
2225 // mt processing
2226 (int) ParallelGCThreads,
2227 // degree of mt processing
2228 (ParallelGCThreads > 1) || (ConcGCThreads > 1),
2229 // mt discovery
2230 (int) MAX2(ParallelGCThreads, ConcGCThreads),
2231 // degree of mt discovery
2232 false,
2233 // Reference discovery is not atomic
2234 &_is_alive_closure_cm,
2235 // is alive closure
2236 // (for efficiency/performance)
2237 true);
2238 // Setting next fields of discovered
2239 // lists requires a barrier.
2240
2241 // STW ref processor
2242 _ref_processor_stw =
2243 new ReferenceProcessor(mr, // span
2244 ParallelRefProcEnabled && (ParallelGCThreads > 1),
2245 // mt processing
2246 MAX2((int)ParallelGCThreads, 1),
2247 // degree of mt processing
2248 (ParallelGCThreads > 1),
2249 // mt discovery
2250 MAX2((int)ParallelGCThreads, 1),
2251 // degree of mt discovery
2252 true,
2253 // Reference discovery is atomic
2254 &_is_alive_closure_stw,
2255 // is alive closure
2256 // (for efficiency/performance)
2257 false);
2258 // Setting next fields of discovered
2259 // lists requires a barrier.
2260 }
2261
2262 size_t G1CollectedHeap::capacity() const {
2263 return _g1_committed.byte_size();
2264 }
2265
2266 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl,
2267 DirtyCardQueue* into_cset_dcq,
2268 bool concurrent,
2269 int worker_i) {
2270 // Clean cards in the hot card cache
2271 concurrent_g1_refine()->clean_up_cache(worker_i, g1_rem_set(), into_cset_dcq);
2272
2273 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
2274 int n_completed_buffers = 0;
2275 while (dcqs.apply_closure_to_completed_buffer(cl, worker_i, 0, true)) {
2276 n_completed_buffers++;
2277 }
2278 g1_policy()->phase_times()->record_update_rs_processed_buffers(worker_i, n_completed_buffers);
2279 dcqs.clear_n_completed_buffers();
2280 assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!");
2281 }
2282
2283
2284 // Computes the sum of the storage used by the various regions.
2285
2286 size_t G1CollectedHeap::used() const {
2287 assert(Heap_lock->owner() != NULL,
2288 "Should be owned on this thread's behalf.");
2289 size_t result = _summary_bytes_used;
2290 // Read only once in case it is set to NULL concurrently
2291 HeapRegion* hr = _mutator_alloc_region.get();
2292 if (hr != NULL)
2293 result += hr->used();
2294 return result;
2295 }
2296
2297 size_t G1CollectedHeap::used_unlocked() const {
2298 size_t result = _summary_bytes_used;
2299 return result;
2300 }
2301
2302 class SumUsedClosure: public HeapRegionClosure {
2303 size_t _used;
2304 public:
2305 SumUsedClosure() : _used(0) {}
2306 bool doHeapRegion(HeapRegion* r) {
2307 if (!r->continuesHumongous()) {
2308 _used += r->used();
2309 }
2310 return false;
2311 }
2312 size_t result() { return _used; }
2313 };
2314
2315 size_t G1CollectedHeap::recalculate_used() const {
2316 SumUsedClosure blk;
2317 heap_region_iterate(&blk);
2318 return blk.result();
2319 }
2320
2321 size_t G1CollectedHeap::unsafe_max_alloc() {
2322 if (free_regions() > 0) return HeapRegion::GrainBytes;
2323 // otherwise, is there space in the current allocation region?
2324
2325 // We need to store the current allocation region in a local variable
2326 // here. The problem is that this method doesn't take any locks and
2327 // there may be other threads which overwrite the current allocation
2328 // region field. attempt_allocation(), for example, sets it to NULL
2329 // and this can happen *after* the NULL check here but before the call
2330 // to free(), resulting in a SIGSEGV. Note that this doesn't appear
2331 // to be a problem in the optimized build, since the two loads of the
2332 // current allocation region field are optimized away.
2333 HeapRegion* hr = _mutator_alloc_region.get();
2334 if (hr == NULL) {
2335 return 0;
2336 }
2337 return hr->free();
2338 }
2339
2340 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) {
2341 switch (cause) {
2342 case GCCause::_gc_locker: return GCLockerInvokesConcurrent;
2343 case GCCause::_java_lang_system_gc: return ExplicitGCInvokesConcurrent;
2344 case GCCause::_g1_humongous_allocation: return true;
2345 default: return false;
2346 }
2347 }
2348
2349 #ifndef PRODUCT
2350 void G1CollectedHeap::allocate_dummy_regions() {
2351 // Let's fill up most of the region
2352 size_t word_size = HeapRegion::GrainWords - 1024;
2353 // And as a result the region we'll allocate will be humongous.
2354 guarantee(isHumongous(word_size), "sanity");
2355
2356 for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) {
2357 // Let's use the existing mechanism for the allocation
2358 HeapWord* dummy_obj = humongous_obj_allocate(word_size);
2359 if (dummy_obj != NULL) {
2360 MemRegion mr(dummy_obj, word_size);
2361 CollectedHeap::fill_with_object(mr);
2362 } else {
2363 // If we can't allocate once, we probably cannot allocate
2364 // again. Let's get out of the loop.
2365 break;
2366 }
2367 }
2368 }
2369 #endif // !PRODUCT
2370
2371 void G1CollectedHeap::increment_old_marking_cycles_started() {
2372 assert(_old_marking_cycles_started == _old_marking_cycles_completed ||
2373 _old_marking_cycles_started == _old_marking_cycles_completed + 1,
2374 err_msg("Wrong marking cycle count (started: %d, completed: %d)",
2375 _old_marking_cycles_started, _old_marking_cycles_completed));
2376
2377 _old_marking_cycles_started++;
2378 }
2379
2380 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) {
2381 MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
2382
2383 // We assume that if concurrent == true, then the caller is a
2384 // concurrent thread that was joined the Suspendible Thread
2385 // Set. If there's ever a cheap way to check this, we should add an
2386 // assert here.
2387
2388 // Given that this method is called at the end of a Full GC or of a
2389 // concurrent cycle, and those can be nested (i.e., a Full GC can
2390 // interrupt a concurrent cycle), the number of full collections
2391 // completed should be either one (in the case where there was no
2392 // nesting) or two (when a Full GC interrupted a concurrent cycle)
2393 // behind the number of full collections started.
2394
2395 // This is the case for the inner caller, i.e. a Full GC.
2396 assert(concurrent ||
2397 (_old_marking_cycles_started == _old_marking_cycles_completed + 1) ||
2398 (_old_marking_cycles_started == _old_marking_cycles_completed + 2),
2399 err_msg("for inner caller (Full GC): _old_marking_cycles_started = %u "
2400 "is inconsistent with _old_marking_cycles_completed = %u",
2401 _old_marking_cycles_started, _old_marking_cycles_completed));
2402
2403 // This is the case for the outer caller, i.e. the concurrent cycle.
2404 assert(!concurrent ||
2405 (_old_marking_cycles_started == _old_marking_cycles_completed + 1),
2406 err_msg("for outer caller (concurrent cycle): "
2407 "_old_marking_cycles_started = %u "
2408 "is inconsistent with _old_marking_cycles_completed = %u",
2409 _old_marking_cycles_started, _old_marking_cycles_completed));
2410
2411 _old_marking_cycles_completed += 1;
2412
2413 // We need to clear the "in_progress" flag in the CM thread before
2414 // we wake up any waiters (especially when ExplicitInvokesConcurrent
2415 // is set) so that if a waiter requests another System.gc() it doesn't
2416 // incorrectly see that a marking cyle is still in progress.
2417 if (concurrent) {
2418 _cmThread->clear_in_progress();
2419 }
2420
2421 // This notify_all() will ensure that a thread that called
2422 // System.gc() with (with ExplicitGCInvokesConcurrent set or not)
2423 // and it's waiting for a full GC to finish will be woken up. It is
2424 // waiting in VM_G1IncCollectionPause::doit_epilogue().
2425 FullGCCount_lock->notify_all();
2426 }
2427
2428 void G1CollectedHeap::collect_as_vm_thread(GCCause::Cause cause) {
2429 assert_at_safepoint(true /* should_be_vm_thread */);
2430 GCCauseSetter gcs(this, cause);
2431 switch (cause) {
2432 case GCCause::_heap_inspection:
2433 case GCCause::_heap_dump: {
2434 HandleMark hm;
2435 do_full_collection(false); // don't clear all soft refs
2436 break;
2437 }
2438 default: // XXX FIX ME
2439 ShouldNotReachHere(); // Unexpected use of this function
2440 }
2441 }
2442
2443 void G1CollectedHeap::collect(GCCause::Cause cause) {
2444 assert_heap_not_locked();
2445
2446 unsigned int gc_count_before;
2447 unsigned int old_marking_count_before;
2448 bool retry_gc;
2449
2450 do {
2451 retry_gc = false;
2452
2453 {
2454 MutexLocker ml(Heap_lock);
2455
2456 // Read the GC count while holding the Heap_lock
2457 gc_count_before = total_collections();
2458 old_marking_count_before = _old_marking_cycles_started;
2459 }
2460
2461 if (should_do_concurrent_full_gc(cause)) {
2462 // Schedule an initial-mark evacuation pause that will start a
2463 // concurrent cycle. We're setting word_size to 0 which means that
2464 // we are not requesting a post-GC allocation.
2465 VM_G1IncCollectionPause op(gc_count_before,
2466 0, /* word_size */
2467 true, /* should_initiate_conc_mark */
2468 g1_policy()->max_pause_time_ms(),
2469 cause);
2470
2471 VMThread::execute(&op);
2472 if (!op.pause_succeeded()) {
2473 if (old_marking_count_before == _old_marking_cycles_started) {
2474 retry_gc = op.should_retry_gc();
2475 } else {
2476 // A Full GC happened while we were trying to schedule the
2477 // initial-mark GC. No point in starting a new cycle given
2478 // that the whole heap was collected anyway.
2479 }
2480
2481 if (retry_gc) {
2482 if (GC_locker::is_active_and_needs_gc()) {
2483 GC_locker::stall_until_clear();
2484 }
2485 }
2486 }
2487 } else {
2488 if (cause == GCCause::_gc_locker
2489 DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) {
2490
2491 // Schedule a standard evacuation pause. We're setting word_size
2492 // to 0 which means that we are not requesting a post-GC allocation.
2493 VM_G1IncCollectionPause op(gc_count_before,
2494 0, /* word_size */
2495 false, /* should_initiate_conc_mark */
2496 g1_policy()->max_pause_time_ms(),
2497 cause);
2498 VMThread::execute(&op);
2499 } else {
2500 // Schedule a Full GC.
2501 VM_G1CollectFull op(gc_count_before, old_marking_count_before, cause);
2502 VMThread::execute(&op);
2503 }
2504 }
2505 } while (retry_gc);
2506 }
2507
2508 bool G1CollectedHeap::is_in(const void* p) const {
2509 if (_g1_committed.contains(p)) {
2510 // Given that we know that p is in the committed space,
2511 // heap_region_containing_raw() should successfully
2512 // return the containing region.
2513 HeapRegion* hr = heap_region_containing_raw(p);
2514 return hr->is_in(p);
2515 } else {
2516 return _perm_gen->as_gen()->is_in(p);
2517 }
2518 }
2519
2520 // Iteration functions.
2521
2522 // Iterates an OopClosure over all ref-containing fields of objects
2523 // within a HeapRegion.
2524
2525 class IterateOopClosureRegionClosure: public HeapRegionClosure {
2526 MemRegion _mr;
2527 OopClosure* _cl;
2528 public:
2529 IterateOopClosureRegionClosure(MemRegion mr, OopClosure* cl)
2530 : _mr(mr), _cl(cl) {}
2531 bool doHeapRegion(HeapRegion* r) {
2532 if (! r->continuesHumongous()) {
2533 r->oop_iterate(_cl);
2534 }
2535 return false;
2536 }
2537 };
2538
2539 void G1CollectedHeap::oop_iterate(OopClosure* cl, bool do_perm) {
2540 IterateOopClosureRegionClosure blk(_g1_committed, cl);
2541 heap_region_iterate(&blk);
2542 if (do_perm) {
2543 perm_gen()->oop_iterate(cl);
2544 }
2545 }
2546
2547 void G1CollectedHeap::oop_iterate(MemRegion mr, OopClosure* cl, bool do_perm) {
2548 IterateOopClosureRegionClosure blk(mr, cl);
2549 heap_region_iterate(&blk);
2550 if (do_perm) {
2551 perm_gen()->oop_iterate(cl);
2552 }
2553 }
2554
2555 // Iterates an ObjectClosure over all objects within a HeapRegion.
2556
2557 class IterateObjectClosureRegionClosure: public HeapRegionClosure {
2558 ObjectClosure* _cl;
2559 public:
2560 IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {}
2561 bool doHeapRegion(HeapRegion* r) {
2562 if (! r->continuesHumongous()) {
2563 r->object_iterate(_cl);
2564 }
2565 return false;
2566 }
2567 };
2568
2569 void G1CollectedHeap::object_iterate(ObjectClosure* cl, bool do_perm) {
2570 IterateObjectClosureRegionClosure blk(cl);
2571 heap_region_iterate(&blk);
2572 if (do_perm) {
2573 perm_gen()->object_iterate(cl);
2574 }
2575 }
2576
2577 void G1CollectedHeap::object_iterate_since_last_GC(ObjectClosure* cl) {
2578 // FIXME: is this right?
2579 guarantee(false, "object_iterate_since_last_GC not supported by G1 heap");
2580 }
2581
2582 // Calls a SpaceClosure on a HeapRegion.
2583
2584 class SpaceClosureRegionClosure: public HeapRegionClosure {
2585 SpaceClosure* _cl;
2586 public:
2587 SpaceClosureRegionClosure(SpaceClosure* cl) : _cl(cl) {}
2588 bool doHeapRegion(HeapRegion* r) {
2589 _cl->do_space(r);
2590 return false;
2591 }
2592 };
2593
2594 void G1CollectedHeap::space_iterate(SpaceClosure* cl) {
2595 SpaceClosureRegionClosure blk(cl);
2596 heap_region_iterate(&blk);
2597 }
2598
2599 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const {
2600 _hrs.iterate(cl);
2601 }
2602
2603 void G1CollectedHeap::heap_region_iterate_from(HeapRegion* r,
2604 HeapRegionClosure* cl) const {
2605 _hrs.iterate_from(r, cl);
2606 }
2607
2608 void
2609 G1CollectedHeap::heap_region_par_iterate_chunked(HeapRegionClosure* cl,
2610 uint worker,
2611 uint no_of_par_workers,
2612 jint claim_value) {
2613 const uint regions = n_regions();
2614 const uint max_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
2615 no_of_par_workers :
2616 1);
2617 assert(UseDynamicNumberOfGCThreads ||
2618 no_of_par_workers == workers()->total_workers(),
2619 "Non dynamic should use fixed number of workers");
2620 // try to spread out the starting points of the workers
2621 const uint start_index = regions / max_workers * worker;
2622
2623 // each worker will actually look at all regions
2624 for (uint count = 0; count < regions; ++count) {
2625 const uint index = (start_index + count) % regions;
2626 assert(0 <= index && index < regions, "sanity");
2627 HeapRegion* r = region_at(index);
2628 // we'll ignore "continues humongous" regions (we'll process them
2629 // when we come across their corresponding "start humongous"
2630 // region) and regions already claimed
2631 if (r->claim_value() == claim_value || r->continuesHumongous()) {
2632 continue;
2633 }
2634 // OK, try to claim it
2635 if (r->claimHeapRegion(claim_value)) {
2636 // success!
2637 assert(!r->continuesHumongous(), "sanity");
2638 if (r->startsHumongous()) {
2639 // If the region is "starts humongous" we'll iterate over its
2640 // "continues humongous" first; in fact we'll do them
2641 // first. The order is important. In on case, calling the
2642 // closure on the "starts humongous" region might de-allocate
2643 // and clear all its "continues humongous" regions and, as a
2644 // result, we might end up processing them twice. So, we'll do
2645 // them first (notice: most closures will ignore them anyway) and
2646 // then we'll do the "starts humongous" region.
2647 for (uint ch_index = index + 1; ch_index < regions; ++ch_index) {
2648 HeapRegion* chr = region_at(ch_index);
2649
2650 // if the region has already been claimed or it's not
2651 // "continues humongous" we're done
2652 if (chr->claim_value() == claim_value ||
2653 !chr->continuesHumongous()) {
2654 break;
2655 }
2656
2657 // Noone should have claimed it directly. We can given
2658 // that we claimed its "starts humongous" region.
2659 assert(chr->claim_value() != claim_value, "sanity");
2660 assert(chr->humongous_start_region() == r, "sanity");
2661
2662 if (chr->claimHeapRegion(claim_value)) {
2663 // we should always be able to claim it; noone else should
2664 // be trying to claim this region
2665
2666 bool res2 = cl->doHeapRegion(chr);
2667 assert(!res2, "Should not abort");
2668
2669 // Right now, this holds (i.e., no closure that actually
2670 // does something with "continues humongous" regions
2671 // clears them). We might have to weaken it in the future,
2672 // but let's leave these two asserts here for extra safety.
2673 assert(chr->continuesHumongous(), "should still be the case");
2674 assert(chr->humongous_start_region() == r, "sanity");
2675 } else {
2676 guarantee(false, "we should not reach here");
2677 }
2678 }
2679 }
2680
2681 assert(!r->continuesHumongous(), "sanity");
2682 bool res = cl->doHeapRegion(r);
2683 assert(!res, "Should not abort");
2684 }
2685 }
2686 }
2687
2688 class ResetClaimValuesClosure: public HeapRegionClosure {
2689 public:
2690 bool doHeapRegion(HeapRegion* r) {
2691 r->set_claim_value(HeapRegion::InitialClaimValue);
2692 return false;
2693 }
2694 };
2695
2696 void G1CollectedHeap::reset_heap_region_claim_values() {
2697 ResetClaimValuesClosure blk;
2698 heap_region_iterate(&blk);
2699 }
2700
2701 void G1CollectedHeap::reset_cset_heap_region_claim_values() {
2702 ResetClaimValuesClosure blk;
2703 collection_set_iterate(&blk);
2704 }
2705
2706 #ifdef ASSERT
2707 // This checks whether all regions in the heap have the correct claim
2708 // value. I also piggy-backed on this a check to ensure that the
2709 // humongous_start_region() information on "continues humongous"
2710 // regions is correct.
2711
2712 class CheckClaimValuesClosure : public HeapRegionClosure {
2713 private:
2714 jint _claim_value;
2715 uint _failures;
2716 HeapRegion* _sh_region;
2717
2718 public:
2719 CheckClaimValuesClosure(jint claim_value) :
2720 _claim_value(claim_value), _failures(0), _sh_region(NULL) { }
2721 bool doHeapRegion(HeapRegion* r) {
2722 if (r->claim_value() != _claim_value) {
2723 gclog_or_tty->print_cr("Region " HR_FORMAT ", "
2724 "claim value = %d, should be %d",
2725 HR_FORMAT_PARAMS(r),
2726 r->claim_value(), _claim_value);
2727 ++_failures;
2728 }
2729 if (!r->isHumongous()) {
2730 _sh_region = NULL;
2731 } else if (r->startsHumongous()) {
2732 _sh_region = r;
2733 } else if (r->continuesHumongous()) {
2734 if (r->humongous_start_region() != _sh_region) {
2735 gclog_or_tty->print_cr("Region " HR_FORMAT ", "
2736 "HS = "PTR_FORMAT", should be "PTR_FORMAT,
2737 HR_FORMAT_PARAMS(r),
2738 r->humongous_start_region(),
2739 _sh_region);
2740 ++_failures;
2741 }
2742 }
2743 return false;
2744 }
2745 uint failures() { return _failures; }
2746 };
2747
2748 bool G1CollectedHeap::check_heap_region_claim_values(jint claim_value) {
2749 CheckClaimValuesClosure cl(claim_value);
2750 heap_region_iterate(&cl);
2751 return cl.failures() == 0;
2752 }
2753
2754 class CheckClaimValuesInCSetHRClosure: public HeapRegionClosure {
2755 private:
2756 jint _claim_value;
2757 uint _failures;
2758
2759 public:
2760 CheckClaimValuesInCSetHRClosure(jint claim_value) :
2761 _claim_value(claim_value), _failures(0) { }
2762
2763 uint failures() { return _failures; }
2764
2765 bool doHeapRegion(HeapRegion* hr) {
2766 assert(hr->in_collection_set(), "how?");
2767 assert(!hr->isHumongous(), "H-region in CSet");
2768 if (hr->claim_value() != _claim_value) {
2769 gclog_or_tty->print_cr("CSet Region " HR_FORMAT ", "
2770 "claim value = %d, should be %d",
2771 HR_FORMAT_PARAMS(hr),
2772 hr->claim_value(), _claim_value);
2773 _failures += 1;
2774 }
2775 return false;
2776 }
2777 };
2778
2779 bool G1CollectedHeap::check_cset_heap_region_claim_values(jint claim_value) {
2780 CheckClaimValuesInCSetHRClosure cl(claim_value);
2781 collection_set_iterate(&cl);
2782 return cl.failures() == 0;
2783 }
2784 #endif // ASSERT
2785
2786 // Clear the cached CSet starting regions and (more importantly)
2787 // the time stamps. Called when we reset the GC time stamp.
2788 void G1CollectedHeap::clear_cset_start_regions() {
2789 assert(_worker_cset_start_region != NULL, "sanity");
2790 assert(_worker_cset_start_region_time_stamp != NULL, "sanity");
2791
2792 int n_queues = MAX2((int)ParallelGCThreads, 1);
2793 for (int i = 0; i < n_queues; i++) {
2794 _worker_cset_start_region[i] = NULL;
2795 _worker_cset_start_region_time_stamp[i] = 0;
2796 }
2797 }
2798
2799 // Given the id of a worker, obtain or calculate a suitable
2800 // starting region for iterating over the current collection set.
2801 HeapRegion* G1CollectedHeap::start_cset_region_for_worker(int worker_i) {
2802 assert(get_gc_time_stamp() > 0, "should have been updated by now");
2803
2804 HeapRegion* result = NULL;
2805 unsigned gc_time_stamp = get_gc_time_stamp();
2806
2807 if (_worker_cset_start_region_time_stamp[worker_i] == gc_time_stamp) {
2808 // Cached starting region for current worker was set
2809 // during the current pause - so it's valid.
2810 // Note: the cached starting heap region may be NULL
2811 // (when the collection set is empty).
2812 result = _worker_cset_start_region[worker_i];
2813 assert(result == NULL || result->in_collection_set(), "sanity");
2814 return result;
2815 }
2816
2817 // The cached entry was not valid so let's calculate
2818 // a suitable starting heap region for this worker.
2819
2820 // We want the parallel threads to start their collection
2821 // set iteration at different collection set regions to
2822 // avoid contention.
2823 // If we have:
2824 // n collection set regions
2825 // p threads
2826 // Then thread t will start at region floor ((t * n) / p)
2827
2828 result = g1_policy()->collection_set();
2829 if (G1CollectedHeap::use_parallel_gc_threads()) {
2830 uint cs_size = g1_policy()->cset_region_length();
2831 uint active_workers = workers()->active_workers();
2832 assert(UseDynamicNumberOfGCThreads ||
2833 active_workers == workers()->total_workers(),
2834 "Unless dynamic should use total workers");
2835
2836 uint end_ind = (cs_size * worker_i) / active_workers;
2837 uint start_ind = 0;
2838
2839 if (worker_i > 0 &&
2840 _worker_cset_start_region_time_stamp[worker_i - 1] == gc_time_stamp) {
2841 // Previous workers starting region is valid
2842 // so let's iterate from there
2843 start_ind = (cs_size * (worker_i - 1)) / active_workers;
2844 result = _worker_cset_start_region[worker_i - 1];
2845 }
2846
2847 for (uint i = start_ind; i < end_ind; i++) {
2848 result = result->next_in_collection_set();
2849 }
2850 }
2851
2852 // Note: the calculated starting heap region may be NULL
2853 // (when the collection set is empty).
2854 assert(result == NULL || result->in_collection_set(), "sanity");
2855 assert(_worker_cset_start_region_time_stamp[worker_i] != gc_time_stamp,
2856 "should be updated only once per pause");
2857 _worker_cset_start_region[worker_i] = result;
2858 OrderAccess::storestore();
2859 _worker_cset_start_region_time_stamp[worker_i] = gc_time_stamp;
2860 return result;
2861 }
2862
2863 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) {
2864 HeapRegion* r = g1_policy()->collection_set();
2865 while (r != NULL) {
2866 HeapRegion* next = r->next_in_collection_set();
2867 if (cl->doHeapRegion(r)) {
2868 cl->incomplete();
2869 return;
2870 }
2871 r = next;
2872 }
2873 }
2874
2875 void G1CollectedHeap::collection_set_iterate_from(HeapRegion* r,
2876 HeapRegionClosure *cl) {
2877 if (r == NULL) {
2878 // The CSet is empty so there's nothing to do.
2879 return;
2880 }
2881
2882 assert(r->in_collection_set(),
2883 "Start region must be a member of the collection set.");
2884 HeapRegion* cur = r;
2885 while (cur != NULL) {
2886 HeapRegion* next = cur->next_in_collection_set();
2887 if (cl->doHeapRegion(cur) && false) {
2888 cl->incomplete();
2889 return;
2890 }
2891 cur = next;
2892 }
2893 cur = g1_policy()->collection_set();
2894 while (cur != r) {
2895 HeapRegion* next = cur->next_in_collection_set();
2896 if (cl->doHeapRegion(cur) && false) {
2897 cl->incomplete();
2898 return;
2899 }
2900 cur = next;
2901 }
2902 }
2903
2904 CompactibleSpace* G1CollectedHeap::first_compactible_space() {
2905 return n_regions() > 0 ? region_at(0) : NULL;
2906 }
2907
2908
2909 Space* G1CollectedHeap::space_containing(const void* addr) const {
2910 Space* res = heap_region_containing(addr);
2911 if (res == NULL)
2912 res = perm_gen()->space_containing(addr);
2913 return res;
2914 }
2915
2916 HeapWord* G1CollectedHeap::block_start(const void* addr) const {
2917 Space* sp = space_containing(addr);
2918 if (sp != NULL) {
2919 return sp->block_start(addr);
2920 }
2921 return NULL;
2922 }
2923
2924 size_t G1CollectedHeap::block_size(const HeapWord* addr) const {
2925 Space* sp = space_containing(addr);
2926 assert(sp != NULL, "block_size of address outside of heap");
2927 return sp->block_size(addr);
2928 }
2929
2930 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const {
2931 Space* sp = space_containing(addr);
2932 return sp->block_is_obj(addr);
2933 }
2934
2935 bool G1CollectedHeap::supports_tlab_allocation() const {
2936 return true;
2937 }
2938
2939 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const {
2940 return HeapRegion::GrainBytes;
2941 }
2942
2943 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const {
2944 // Return the remaining space in the cur alloc region, but not less than
2945 // the min TLAB size.
2946
2947 // Also, this value can be at most the humongous object threshold,
2948 // since we can't allow tlabs to grow big enough to accomodate
2949 // humongous objects.
2950
2951 HeapRegion* hr = _mutator_alloc_region.get();
2952 size_t max_tlab_size = _humongous_object_threshold_in_words * wordSize;
2953 if (hr == NULL) {
2954 return max_tlab_size;
2955 } else {
2956 return MIN2(MAX2(hr->free(), (size_t) MinTLABSize), max_tlab_size);
2957 }
2958 }
2959
2960 size_t G1CollectedHeap::max_capacity() const {
2961 return _g1_reserved.byte_size();
2962 }
2963
2964 jlong G1CollectedHeap::millis_since_last_gc() {
2965 // assert(false, "NYI");
2966 return 0;
2967 }
2968
2969 void G1CollectedHeap::prepare_for_verify() {
2970 if (SafepointSynchronize::is_at_safepoint() || ! UseTLAB) {
2971 ensure_parsability(false);
2972 }
2973 g1_rem_set()->prepare_for_verify();
2974 }
2975
2976 class VerifyLivenessOopClosure: public OopClosure {
2977 G1CollectedHeap* _g1h;
2978 VerifyOption _vo;
2979 public:
2980 VerifyLivenessOopClosure(G1CollectedHeap* g1h, VerifyOption vo):
2981 _g1h(g1h), _vo(vo)
2982 { }
2983 void do_oop(narrowOop *p) { do_oop_work(p); }
2984 void do_oop( oop *p) { do_oop_work(p); }
2985
2986 template <class T> void do_oop_work(T *p) {
2987 oop obj = oopDesc::load_decode_heap_oop(p);
2988 guarantee(obj == NULL || !_g1h->is_obj_dead_cond(obj, _vo),
2989 "Dead object referenced by a not dead object");
2990 }
2991 };
2992
2993 class VerifyObjsInRegionClosure: public ObjectClosure {
2994 private:
2995 G1CollectedHeap* _g1h;
2996 size_t _live_bytes;
2997 HeapRegion *_hr;
2998 VerifyOption _vo;
2999 public:
3000 // _vo == UsePrevMarking -> use "prev" marking information,
3001 // _vo == UseNextMarking -> use "next" marking information,
3002 // _vo == UseMarkWord -> use mark word from object header.
3003 VerifyObjsInRegionClosure(HeapRegion *hr, VerifyOption vo)
3004 : _live_bytes(0), _hr(hr), _vo(vo) {
3005 _g1h = G1CollectedHeap::heap();
3006 }
3007 void do_object(oop o) {
3008 VerifyLivenessOopClosure isLive(_g1h, _vo);
3009 assert(o != NULL, "Huh?");
3010 if (!_g1h->is_obj_dead_cond(o, _vo)) {
3011 // If the object is alive according to the mark word,
3012 // then verify that the marking information agrees.
3013 // Note we can't verify the contra-positive of the
3014 // above: if the object is dead (according to the mark
3015 // word), it may not be marked, or may have been marked
3016 // but has since became dead, or may have been allocated
3017 // since the last marking.
3018 if (_vo == VerifyOption_G1UseMarkWord) {
3019 guarantee(!_g1h->is_obj_dead(o), "mark word and concurrent mark mismatch");
3020 }
3021
3022 o->oop_iterate(&isLive);
3023 if (!_hr->obj_allocated_since_prev_marking(o)) {
3024 size_t obj_size = o->size(); // Make sure we don't overflow
3025 _live_bytes += (obj_size * HeapWordSize);
3026 }
3027 }
3028 }
3029 size_t live_bytes() { return _live_bytes; }
3030 };
3031
3032 class PrintObjsInRegionClosure : public ObjectClosure {
3033 HeapRegion *_hr;
3034 G1CollectedHeap *_g1;
3035 public:
3036 PrintObjsInRegionClosure(HeapRegion *hr) : _hr(hr) {
3037 _g1 = G1CollectedHeap::heap();
3038 };
3039
3040 void do_object(oop o) {
3041 if (o != NULL) {
3042 HeapWord *start = (HeapWord *) o;
3043 size_t word_sz = o->size();
3044 gclog_or_tty->print("\nPrinting obj "PTR_FORMAT" of size " SIZE_FORMAT
3045 " isMarkedPrev %d isMarkedNext %d isAllocSince %d\n",
3046 (void*) o, word_sz,
3047 _g1->isMarkedPrev(o),
3048 _g1->isMarkedNext(o),
3049 _hr->obj_allocated_since_prev_marking(o));
3050 HeapWord *end = start + word_sz;
3051 HeapWord *cur;
3052 int *val;
3053 for (cur = start; cur < end; cur++) {
3054 val = (int *) cur;
3055 gclog_or_tty->print("\t "PTR_FORMAT":"PTR_FORMAT"\n", val, *val);
3056 }
3057 }
3058 }
3059 };
3060
3061 class VerifyRegionClosure: public HeapRegionClosure {
3062 private:
3063 bool _par;
3064 VerifyOption _vo;
3065 bool _failures;
3066 public:
3067 // _vo == UsePrevMarking -> use "prev" marking information,
3068 // _vo == UseNextMarking -> use "next" marking information,
3069 // _vo == UseMarkWord -> use mark word from object header.
3070 VerifyRegionClosure(bool par, VerifyOption vo)
3071 : _par(par),
3072 _vo(vo),
3073 _failures(false) {}
3074
3075 bool failures() {
3076 return _failures;
3077 }
3078
3079 bool doHeapRegion(HeapRegion* r) {
3080 guarantee(_par || r->claim_value() == HeapRegion::InitialClaimValue,
3081 "Should be unclaimed at verify points.");
3082 if (!r->continuesHumongous()) {
3083 bool failures = false;
3084 r->verify(_vo, &failures);
3085 if (failures) {
3086 _failures = true;
3087 } else {
3088 VerifyObjsInRegionClosure not_dead_yet_cl(r, _vo);
3089 r->object_iterate(¬_dead_yet_cl);
3090 if (_vo != VerifyOption_G1UseNextMarking) {
3091 if (r->max_live_bytes() < not_dead_yet_cl.live_bytes()) {
3092 gclog_or_tty->print_cr("["PTR_FORMAT","PTR_FORMAT"] "
3093 "max_live_bytes "SIZE_FORMAT" "
3094 "< calculated "SIZE_FORMAT,
3095 r->bottom(), r->end(),
3096 r->max_live_bytes(),
3097 not_dead_yet_cl.live_bytes());
3098 _failures = true;
3099 }
3100 } else {
3101 // When vo == UseNextMarking we cannot currently do a sanity
3102 // check on the live bytes as the calculation has not been
3103 // finalized yet.
3104 }
3105 }
3106 }
3107 return false; // stop the region iteration if we hit a failure
3108 }
3109 };
3110
3111 class VerifyRootsClosure: public OopsInGenClosure {
3112 private:
3113 G1CollectedHeap* _g1h;
3114 VerifyOption _vo;
3115 bool _failures;
3116 public:
3117 // _vo == UsePrevMarking -> use "prev" marking information,
3118 // _vo == UseNextMarking -> use "next" marking information,
3119 // _vo == UseMarkWord -> use mark word from object header.
3120 VerifyRootsClosure(VerifyOption vo) :
3121 _g1h(G1CollectedHeap::heap()),
3122 _vo(vo),
3123 _failures(false) { }
3124
3125 bool failures() { return _failures; }
3126
3127 template <class T> void do_oop_nv(T* p) {
3128 T heap_oop = oopDesc::load_heap_oop(p);
3129 if (!oopDesc::is_null(heap_oop)) {
3130 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
3131 if (_g1h->is_obj_dead_cond(obj, _vo)) {
3132 gclog_or_tty->print_cr("Root location "PTR_FORMAT" "
3133 "points to dead obj "PTR_FORMAT, p, (void*) obj);
3134 if (_vo == VerifyOption_G1UseMarkWord) {
3135 gclog_or_tty->print_cr(" Mark word: "PTR_FORMAT, (void*)(obj->mark()));
3136 }
3137 obj->print_on(gclog_or_tty);
3138 _failures = true;
3139 }
3140 }
3141 }
3142
3143 void do_oop(oop* p) { do_oop_nv(p); }
3144 void do_oop(narrowOop* p) { do_oop_nv(p); }
3145 };
3146
3147 // This is the task used for parallel heap verification.
3148
3149 class G1ParVerifyTask: public AbstractGangTask {
3150 private:
3151 G1CollectedHeap* _g1h;
3152 VerifyOption _vo;
3153 bool _failures;
3154
3155 public:
3156 // _vo == UsePrevMarking -> use "prev" marking information,
3157 // _vo == UseNextMarking -> use "next" marking information,
3158 // _vo == UseMarkWord -> use mark word from object header.
3159 G1ParVerifyTask(G1CollectedHeap* g1h, VerifyOption vo) :
3160 AbstractGangTask("Parallel verify task"),
3161 _g1h(g1h),
3162 _vo(vo),
3163 _failures(false) { }
3164
3165 bool failures() {
3166 return _failures;
3167 }
3168
3169 void work(uint worker_id) {
3170 HandleMark hm;
3171 VerifyRegionClosure blk(true, _vo);
3172 _g1h->heap_region_par_iterate_chunked(&blk, worker_id,
3173 _g1h->workers()->active_workers(),
3174 HeapRegion::ParVerifyClaimValue);
3175 if (blk.failures()) {
3176 _failures = true;
3177 }
3178 }
3179 };
3180
3181 void G1CollectedHeap::verify(bool silent) {
3182 verify(silent, VerifyOption_G1UsePrevMarking);
3183 }
3184
3185 void G1CollectedHeap::verify(bool silent,
3186 VerifyOption vo) {
3187 if (SafepointSynchronize::is_at_safepoint() || ! UseTLAB) {
3188 if (!silent) { gclog_or_tty->print("Roots (excluding permgen) "); }
3189 VerifyRootsClosure rootsCl(vo);
3190
3191 assert(Thread::current()->is_VM_thread(),
3192 "Expected to be executed serially by the VM thread at this point");
3193
3194 CodeBlobToOopClosure blobsCl(&rootsCl, /*do_marking=*/ false);
3195
3196 // We apply the relevant closures to all the oops in the
3197 // system dictionary, the string table and the code cache.
3198 const int so = SO_AllClasses | SO_Strings | SO_CodeCache;
3199
3200 process_strong_roots(true, // activate StrongRootsScope
3201 true, // we set "collecting perm gen" to true,
3202 // so we don't reset the dirty cards in the perm gen.
3203 ScanningOption(so), // roots scanning options
3204 &rootsCl,
3205 &blobsCl,
3206 &rootsCl);
3207
3208 // If we're verifying after the marking phase of a Full GC then we can't
3209 // treat the perm gen as roots into the G1 heap. Some of the objects in
3210 // the perm gen may be dead and hence not marked. If one of these dead
3211 // objects is considered to be a root then we may end up with a false
3212 // "Root location <x> points to dead ob <y>" failure.
3213 if (vo != VerifyOption_G1UseMarkWord) {
3214 // Since we used "collecting_perm_gen" == true above, we will not have
3215 // checked the refs from perm into the G1-collected heap. We check those
3216 // references explicitly below. Whether the relevant cards are dirty
3217 // is checked further below in the rem set verification.
3218 if (!silent) { gclog_or_tty->print("Permgen roots "); }
3219 perm_gen()->oop_iterate(&rootsCl);
3220 }
3221 bool failures = rootsCl.failures();
3222
3223 if (vo != VerifyOption_G1UseMarkWord) {
3224 // If we're verifying during a full GC then the region sets
3225 // will have been torn down at the start of the GC. Therefore
3226 // verifying the region sets will fail. So we only verify
3227 // the region sets when not in a full GC.
3228 if (!silent) { gclog_or_tty->print("HeapRegionSets "); }
3229 verify_region_sets();
3230 }
3231
3232 if (!silent) { gclog_or_tty->print("HeapRegions "); }
3233 if (GCParallelVerificationEnabled && ParallelGCThreads > 1) {
3234 assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue),
3235 "sanity check");
3236
3237 G1ParVerifyTask task(this, vo);
3238 assert(UseDynamicNumberOfGCThreads ||
3239 workers()->active_workers() == workers()->total_workers(),
3240 "If not dynamic should be using all the workers");
3241 int n_workers = workers()->active_workers();
3242 set_par_threads(n_workers);
3243 workers()->run_task(&task);
3244 set_par_threads(0);
3245 if (task.failures()) {
3246 failures = true;
3247 }
3248
3249 // Checks that the expected amount of parallel work was done.
3250 // The implication is that n_workers is > 0.
3251 assert(check_heap_region_claim_values(HeapRegion::ParVerifyClaimValue),
3252 "sanity check");
3253
3254 reset_heap_region_claim_values();
3255
3256 assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue),
3257 "sanity check");
3258 } else {
3259 VerifyRegionClosure blk(false, vo);
3260 heap_region_iterate(&blk);
3261 if (blk.failures()) {
3262 failures = true;
3263 }
3264 }
3265 if (!silent) gclog_or_tty->print("RemSet ");
3266 rem_set()->verify();
3267
3268 if (failures) {
3269 gclog_or_tty->print_cr("Heap:");
3270 // It helps to have the per-region information in the output to
3271 // help us track down what went wrong. This is why we call
3272 // print_extended_on() instead of print_on().
3273 print_extended_on(gclog_or_tty);
3274 gclog_or_tty->print_cr("");
3275 #ifndef PRODUCT
3276 if (VerifyDuringGC && G1VerifyDuringGCPrintReachable) {
3277 concurrent_mark()->print_reachable("at-verification-failure",
3278 vo, false /* all */);
3279 }
3280 #endif
3281 gclog_or_tty->flush();
3282 }
3283 guarantee(!failures, "there should not have been any failures");
3284 } else {
3285 if (!silent) gclog_or_tty->print("(SKIPPING roots, heapRegions, remset) ");
3286 }
3287 }
3288
3289 class PrintRegionClosure: public HeapRegionClosure {
3290 outputStream* _st;
3291 public:
3292 PrintRegionClosure(outputStream* st) : _st(st) {}
3293 bool doHeapRegion(HeapRegion* r) {
3294 r->print_on(_st);
3295 return false;
3296 }
3297 };
3298
3299 void G1CollectedHeap::print_on(outputStream* st) const {
3300 st->print(" %-20s", "garbage-first heap");
3301 st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K",
3302 capacity()/K, used_unlocked()/K);
3303 st->print(" [" INTPTR_FORMAT ", " INTPTR_FORMAT ", " INTPTR_FORMAT ")",
3304 _g1_storage.low_boundary(),
3305 _g1_storage.high(),
3306 _g1_storage.high_boundary());
3307 st->cr();
3308 st->print(" region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K);
3309 uint young_regions = _young_list->length();
3310 st->print("%u young (" SIZE_FORMAT "K), ", young_regions,
3311 (size_t) young_regions * HeapRegion::GrainBytes / K);
3312 uint survivor_regions = g1_policy()->recorded_survivor_regions();
3313 st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions,
3314 (size_t) survivor_regions * HeapRegion::GrainBytes / K);
3315 st->cr();
3316 perm()->as_gen()->print_on(st);
3317 }
3318
3319 void G1CollectedHeap::print_extended_on(outputStream* st) const {
3320 print_on(st);
3321
3322 // Print the per-region information.
3323 st->cr();
3324 st->print_cr("Heap Regions: (Y=young(eden), SU=young(survivor), "
3325 "HS=humongous(starts), HC=humongous(continues), "
3326 "CS=collection set, F=free, TS=gc time stamp, "
3327 "PTAMS=previous top-at-mark-start, "
3328 "NTAMS=next top-at-mark-start)");
3329 PrintRegionClosure blk(st);
3330 heap_region_iterate(&blk);
3331 }
3332
3333 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const {
3334 if (G1CollectedHeap::use_parallel_gc_threads()) {
3335 workers()->print_worker_threads_on(st);
3336 }
3337 _cmThread->print_on(st);
3338 st->cr();
3339 _cm->print_worker_threads_on(st);
3340 _cg1r->print_worker_threads_on(st);
3341 st->cr();
3342 }
3343
3344 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const {
3345 if (G1CollectedHeap::use_parallel_gc_threads()) {
3346 workers()->threads_do(tc);
3347 }
3348 tc->do_thread(_cmThread);
3349 _cg1r->threads_do(tc);
3350 }
3351
3352 void G1CollectedHeap::print_tracing_info() const {
3353 // We'll overload this to mean "trace GC pause statistics."
3354 if (TraceGen0Time || TraceGen1Time) {
3355 // The "G1CollectorPolicy" is keeping track of these stats, so delegate
3356 // to that.
3357 g1_policy()->print_tracing_info();
3358 }
3359 if (G1SummarizeRSetStats) {
3360 g1_rem_set()->print_summary_info();
3361 }
3362 if (G1SummarizeConcMark) {
3363 concurrent_mark()->print_summary_info();
3364 }
3365 g1_policy()->print_yg_surv_rate_info();
3366 SpecializationStats::print();
3367 }
3368
3369 #ifndef PRODUCT
3370 // Helpful for debugging RSet issues.
3371
3372 class PrintRSetsClosure : public HeapRegionClosure {
3373 private:
3374 const char* _msg;
3375 size_t _occupied_sum;
3376
3377 public:
3378 bool doHeapRegion(HeapRegion* r) {
3379 HeapRegionRemSet* hrrs = r->rem_set();
3380 size_t occupied = hrrs->occupied();
3381 _occupied_sum += occupied;
3382
3383 gclog_or_tty->print_cr("Printing RSet for region "HR_FORMAT,
3384 HR_FORMAT_PARAMS(r));
3385 if (occupied == 0) {
3386 gclog_or_tty->print_cr(" RSet is empty");
3387 } else {
3388 hrrs->print();
3389 }
3390 gclog_or_tty->print_cr("----------");
3391 return false;
3392 }
3393
3394 PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) {
3395 gclog_or_tty->cr();
3396 gclog_or_tty->print_cr("========================================");
3397 gclog_or_tty->print_cr(msg);
3398 gclog_or_tty->cr();
3399 }
3400
3401 ~PrintRSetsClosure() {
3402 gclog_or_tty->print_cr("Occupied Sum: "SIZE_FORMAT, _occupied_sum);
3403 gclog_or_tty->print_cr("========================================");
3404 gclog_or_tty->cr();
3405 }
3406 };
3407
3408 void G1CollectedHeap::print_cset_rsets() {
3409 PrintRSetsClosure cl("Printing CSet RSets");
3410 collection_set_iterate(&cl);
3411 }
3412
3413 void G1CollectedHeap::print_all_rsets() {
3414 PrintRSetsClosure cl("Printing All RSets");;
3415 heap_region_iterate(&cl);
3416 }
3417 #endif // PRODUCT
3418
3419 G1CollectedHeap* G1CollectedHeap::heap() {
3420 assert(_sh->kind() == CollectedHeap::G1CollectedHeap,
3421 "not a garbage-first heap");
3422 return _g1h;
3423 }
3424
3425 void G1CollectedHeap::gc_prologue(bool full /* Ignored */) {
3426 // always_do_update_barrier = false;
3427 assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
3428 // Call allocation profiler
3429 AllocationProfiler::iterate_since_last_gc();
3430 // Fill TLAB's and such
3431 ensure_parsability(true);
3432 }
3433
3434 void G1CollectedHeap::gc_epilogue(bool full /* Ignored */) {
3435 // FIXME: what is this about?
3436 // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled"
3437 // is set.
3438 COMPILER2_PRESENT(assert(DerivedPointerTable::is_empty(),
3439 "derived pointer present"));
3440 // always_do_update_barrier = true;
3441
3442 // We have just completed a GC. Update the soft reference
3443 // policy with the new heap occupancy
3444 Universe::update_heap_info_at_gc();
3445 }
3446
3447 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size,
3448 unsigned int gc_count_before,
3449 bool* succeeded) {
3450 assert_heap_not_locked_and_not_at_safepoint();
3451 g1_policy()->record_stop_world_start();
3452 VM_G1IncCollectionPause op(gc_count_before,
3453 word_size,
3454 false, /* should_initiate_conc_mark */
3455 g1_policy()->max_pause_time_ms(),
3456 GCCause::_g1_inc_collection_pause);
3457 VMThread::execute(&op);
3458
3459 HeapWord* result = op.result();
3460 bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded();
3461 assert(result == NULL || ret_succeeded,
3462 "the result should be NULL if the VM did not succeed");
3463 *succeeded = ret_succeeded;
3464
3465 assert_heap_not_locked();
3466 return result;
3467 }
3468
3469 void
3470 G1CollectedHeap::doConcurrentMark() {
3471 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
3472 if (!_cmThread->in_progress()) {
3473 _cmThread->set_started();
3474 CGC_lock->notify();
3475 }
3476 }
3477
3478 size_t G1CollectedHeap::pending_card_num() {
3479 size_t extra_cards = 0;
3480 JavaThread *curr = Threads::first();
3481 while (curr != NULL) {
3482 DirtyCardQueue& dcq = curr->dirty_card_queue();
3483 extra_cards += dcq.size();
3484 curr = curr->next();
3485 }
3486 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
3487 size_t buffer_size = dcqs.buffer_size();
3488 size_t buffer_num = dcqs.completed_buffers_num();
3489 return buffer_size * buffer_num + extra_cards;
3490 }
3491
3492 size_t G1CollectedHeap::max_pending_card_num() {
3493 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
3494 size_t buffer_size = dcqs.buffer_size();
3495 size_t buffer_num = dcqs.completed_buffers_num();
3496 int thread_num = Threads::number_of_threads();
3497 return (buffer_num + thread_num) * buffer_size;
3498 }
3499
3500 size_t G1CollectedHeap::cards_scanned() {
3501 return g1_rem_set()->cardsScanned();
3502 }
3503
3504 void
3505 G1CollectedHeap::setup_surviving_young_words() {
3506 assert(_surviving_young_words == NULL, "pre-condition");
3507 uint array_length = g1_policy()->young_cset_region_length();
3508 _surviving_young_words = NEW_C_HEAP_ARRAY(size_t, (size_t) array_length, mtGC);
3509 if (_surviving_young_words == NULL) {
3510 vm_exit_out_of_memory(sizeof(size_t) * array_length,
3511 "Not enough space for young surv words summary.");
3512 }
3513 memset(_surviving_young_words, 0, (size_t) array_length * sizeof(size_t));
3514 #ifdef ASSERT
3515 for (uint i = 0; i < array_length; ++i) {
3516 assert( _surviving_young_words[i] == 0, "memset above" );
3517 }
3518 #endif // !ASSERT
3519 }
3520
3521 void
3522 G1CollectedHeap::update_surviving_young_words(size_t* surv_young_words) {
3523 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
3524 uint array_length = g1_policy()->young_cset_region_length();
3525 for (uint i = 0; i < array_length; ++i) {
3526 _surviving_young_words[i] += surv_young_words[i];
3527 }
3528 }
3529
3530 void
3531 G1CollectedHeap::cleanup_surviving_young_words() {
3532 guarantee( _surviving_young_words != NULL, "pre-condition" );
3533 FREE_C_HEAP_ARRAY(size_t, _surviving_young_words, mtGC);
3534 _surviving_young_words = NULL;
3535 }
3536
3537 #ifdef ASSERT
3538 class VerifyCSetClosure: public HeapRegionClosure {
3539 public:
3540 bool doHeapRegion(HeapRegion* hr) {
3541 // Here we check that the CSet region's RSet is ready for parallel
3542 // iteration. The fields that we'll verify are only manipulated
3543 // when the region is part of a CSet and is collected. Afterwards,
3544 // we reset these fields when we clear the region's RSet (when the
3545 // region is freed) so they are ready when the region is
3546 // re-allocated. The only exception to this is if there's an
3547 // evacuation failure and instead of freeing the region we leave
3548 // it in the heap. In that case, we reset these fields during
3549 // evacuation failure handling.
3550 guarantee(hr->rem_set()->verify_ready_for_par_iteration(), "verification");
3551
3552 // Here's a good place to add any other checks we'd like to
3553 // perform on CSet regions.
3554 return false;
3555 }
3556 };
3557 #endif // ASSERT
3558
3559 #if TASKQUEUE_STATS
3560 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) {
3561 st->print_raw_cr("GC Task Stats");
3562 st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr();
3563 st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr();
3564 }
3565
3566 void G1CollectedHeap::print_taskqueue_stats(outputStream* const st) const {
3567 print_taskqueue_stats_hdr(st);
3568
3569 TaskQueueStats totals;
3570 const int n = workers() != NULL ? workers()->total_workers() : 1;
3571 for (int i = 0; i < n; ++i) {
3572 st->print("%3d ", i); task_queue(i)->stats.print(st); st->cr();
3573 totals += task_queue(i)->stats;
3574 }
3575 st->print_raw("tot "); totals.print(st); st->cr();
3576
3577 DEBUG_ONLY(totals.verify());
3578 }
3579
3580 void G1CollectedHeap::reset_taskqueue_stats() {
3581 const int n = workers() != NULL ? workers()->total_workers() : 1;
3582 for (int i = 0; i < n; ++i) {
3583 task_queue(i)->stats.reset();
3584 }
3585 }
3586 #endif // TASKQUEUE_STATS
3587
3588 bool
3589 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) {
3590 assert_at_safepoint(true /* should_be_vm_thread */);
3591 guarantee(!is_gc_active(), "collection is not reentrant");
3592
3593 if (GC_locker::check_active_before_gc()) {
3594 return false;
3595 }
3596
3597 SvcGCMarker sgcm(SvcGCMarker::MINOR);
3598 ResourceMark rm;
3599
3600 print_heap_before_gc();
3601
3602 HRSPhaseSetter x(HRSPhaseEvacuation);
3603 verify_region_sets_optional();
3604 verify_dirty_young_regions();
3605
3606 // This call will decide whether this pause is an initial-mark
3607 // pause. If it is, during_initial_mark_pause() will return true
3608 // for the duration of this pause.
3609 g1_policy()->decide_on_conc_mark_initiation();
3610
3611 // We do not allow initial-mark to be piggy-backed on a mixed GC.
3612 assert(!g1_policy()->during_initial_mark_pause() ||
3613 g1_policy()->gcs_are_young(), "sanity");
3614
3615 // We also do not allow mixed GCs during marking.
3616 assert(!mark_in_progress() || g1_policy()->gcs_are_young(), "sanity");
3617
3618 // Record whether this pause is an initial mark. When the current
3619 // thread has completed its logging output and it's safe to signal
3620 // the CM thread, the flag's value in the policy has been reset.
3621 bool should_start_conc_mark = g1_policy()->during_initial_mark_pause();
3622
3623 // Inner scope for scope based logging, timers, and stats collection
3624 {
3625 if (g1_policy()->during_initial_mark_pause()) {
3626 // We are about to start a marking cycle, so we increment the
3627 // full collection counter.
3628 increment_old_marking_cycles_started();
3629 }
3630 // if the log level is "finer" is on, we'll print long statistics information
3631 // in the collector policy code, so let's not print this as the output
3632 // is messy if we do.
3633 gclog_or_tty->date_stamp(G1Log::fine() && PrintGCDateStamps);
3634 TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty);
3635
3636 int active_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
3637 workers()->active_workers() : 1);
3638 g1_policy()->phase_times()->note_gc_start(os::elapsedTime(), active_workers,
3639 g1_policy()->gcs_are_young(), g1_policy()->during_initial_mark_pause(), gc_cause());
3640
3641 TraceCollectorStats tcs(g1mm()->incremental_collection_counters());
3642 TraceMemoryManagerStats tms(false /* fullGC */, gc_cause());
3643
3644 // If the secondary_free_list is not empty, append it to the
3645 // free_list. No need to wait for the cleanup operation to finish;
3646 // the region allocation code will check the secondary_free_list
3647 // and wait if necessary. If the G1StressConcRegionFreeing flag is
3648 // set, skip this step so that the region allocation code has to
3649 // get entries from the secondary_free_list.
3650 if (!G1StressConcRegionFreeing) {
3651 append_secondary_free_list_if_not_empty_with_lock();
3652 }
3653
3654 assert(check_young_list_well_formed(),
3655 "young list should be well formed");
3656
3657 // Don't dynamically change the number of GC threads this early. A value of
3658 // 0 is used to indicate serial work. When parallel work is done,
3659 // it will be set.
3660
3661 { // Call to jvmpi::post_class_unload_events must occur outside of active GC
3662 IsGCActiveMark x;
3663
3664 gc_prologue(false);
3665 increment_total_collections(false /* full gc */);
3666 increment_gc_time_stamp();
3667
3668 if (VerifyBeforeGC && total_collections() >= VerifyGCStartAt) {
3669 HandleMark hm; // Discard invalid handles created during verification
3670 gclog_or_tty->print(" VerifyBeforeGC:");
3671 prepare_for_verify();
3672 Universe::verify(/* silent */ false,
3673 /* option */ VerifyOption_G1UsePrevMarking);
3674 }
3675
3676 COMPILER2_PRESENT(DerivedPointerTable::clear());
3677
3678 // Please see comment in g1CollectedHeap.hpp and
3679 // G1CollectedHeap::ref_processing_init() to see how
3680 // reference processing currently works in G1.
3681
3682 // Enable discovery in the STW reference processor
3683 ref_processor_stw()->enable_discovery(true /*verify_disabled*/,
3684 true /*verify_no_refs*/);
3685
3686 {
3687 // We want to temporarily turn off discovery by the
3688 // CM ref processor, if necessary, and turn it back on
3689 // on again later if we do. Using a scoped
3690 // NoRefDiscovery object will do this.
3691 NoRefDiscovery no_cm_discovery(ref_processor_cm());
3692
3693 // Forget the current alloc region (we might even choose it to be part
3694 // of the collection set!).
3695 release_mutator_alloc_region();
3696
3697 // We should call this after we retire the mutator alloc
3698 // region(s) so that all the ALLOC / RETIRE events are generated
3699 // before the start GC event.
3700 _hr_printer.start_gc(false /* full */, (size_t) total_collections());
3701
3702 // This timing is only used by the ergonomics to handle our pause target.
3703 // It is unclear why this should not include the full pause. We will
3704 // investigate this in CR 7178365.
3705 //
3706 // Preserving the old comment here if that helps the investigation:
3707 //
3708 // The elapsed time induced by the start time below deliberately elides
3709 // the possible verification above.
3710 double sample_start_time_sec = os::elapsedTime();
3711 size_t start_used_bytes = used();
3712
3713 #if YOUNG_LIST_VERBOSE
3714 gclog_or_tty->print_cr("\nBefore recording pause start.\nYoung_list:");
3715 _young_list->print();
3716 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
3717 #endif // YOUNG_LIST_VERBOSE
3718
3719 g1_policy()->record_collection_pause_start(sample_start_time_sec,
3720 start_used_bytes);
3721
3722 double scan_wait_start = os::elapsedTime();
3723 // We have to wait until the CM threads finish scanning the
3724 // root regions as it's the only way to ensure that all the
3725 // objects on them have been correctly scanned before we start
3726 // moving them during the GC.
3727 bool waited = _cm->root_regions()->wait_until_scan_finished();
3728 double wait_time_ms = 0.0;
3729 if (waited) {
3730 double scan_wait_end = os::elapsedTime();
3731 wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0;
3732 }
3733 g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms);
3734
3735 #if YOUNG_LIST_VERBOSE
3736 gclog_or_tty->print_cr("\nAfter recording pause start.\nYoung_list:");
3737 _young_list->print();
3738 #endif // YOUNG_LIST_VERBOSE
3739
3740 if (g1_policy()->during_initial_mark_pause()) {
3741 concurrent_mark()->checkpointRootsInitialPre();
3742 }
3743 perm_gen()->save_marks();
3744
3745 #if YOUNG_LIST_VERBOSE
3746 gclog_or_tty->print_cr("\nBefore choosing collection set.\nYoung_list:");
3747 _young_list->print();
3748 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
3749 #endif // YOUNG_LIST_VERBOSE
3750
3751 g1_policy()->finalize_cset(target_pause_time_ms);
3752
3753 _cm->note_start_of_gc();
3754 // We should not verify the per-thread SATB buffers given that
3755 // we have not filtered them yet (we'll do so during the
3756 // GC). We also call this after finalize_cset() to
3757 // ensure that the CSet has been finalized.
3758 _cm->verify_no_cset_oops(true /* verify_stacks */,
3759 true /* verify_enqueued_buffers */,
3760 false /* verify_thread_buffers */,
3761 true /* verify_fingers */);
3762
3763 if (_hr_printer.is_active()) {
3764 HeapRegion* hr = g1_policy()->collection_set();
3765 while (hr != NULL) {
3766 G1HRPrinter::RegionType type;
3767 if (!hr->is_young()) {
3768 type = G1HRPrinter::Old;
3769 } else if (hr->is_survivor()) {
3770 type = G1HRPrinter::Survivor;
3771 } else {
3772 type = G1HRPrinter::Eden;
3773 }
3774 _hr_printer.cset(hr);
3775 hr = hr->next_in_collection_set();
3776 }
3777 }
3778
3779 #ifdef ASSERT
3780 VerifyCSetClosure cl;
3781 collection_set_iterate(&cl);
3782 #endif // ASSERT
3783
3784 setup_surviving_young_words();
3785
3786 // Initialize the GC alloc regions.
3787 init_gc_alloc_regions();
3788
3789 // Actually do the work...
3790 evacuate_collection_set();
3791
3792 // We do this to mainly verify the per-thread SATB buffers
3793 // (which have been filtered by now) since we didn't verify
3794 // them earlier. No point in re-checking the stacks / enqueued
3795 // buffers given that the CSet has not changed since last time
3796 // we checked.
3797 _cm->verify_no_cset_oops(false /* verify_stacks */,
3798 false /* verify_enqueued_buffers */,
3799 true /* verify_thread_buffers */,
3800 true /* verify_fingers */);
3801
3802 free_collection_set(g1_policy()->collection_set());
3803 g1_policy()->clear_collection_set();
3804
3805 cleanup_surviving_young_words();
3806
3807 // Start a new incremental collection set for the next pause.
3808 g1_policy()->start_incremental_cset_building();
3809
3810 // Clear the _cset_fast_test bitmap in anticipation of adding
3811 // regions to the incremental collection set for the next
3812 // evacuation pause.
3813 clear_cset_fast_test();
3814
3815 _young_list->reset_sampled_info();
3816
3817 // Don't check the whole heap at this point as the
3818 // GC alloc regions from this pause have been tagged
3819 // as survivors and moved on to the survivor list.
3820 // Survivor regions will fail the !is_young() check.
3821 assert(check_young_list_empty(false /* check_heap */),
3822 "young list should be empty");
3823
3824 #if YOUNG_LIST_VERBOSE
3825 gclog_or_tty->print_cr("Before recording survivors.\nYoung List:");
3826 _young_list->print();
3827 #endif // YOUNG_LIST_VERBOSE
3828
3829 g1_policy()->record_survivor_regions(_young_list->survivor_length(),
3830 _young_list->first_survivor_region(),
3831 _young_list->last_survivor_region());
3832
3833 _young_list->reset_auxilary_lists();
3834
3835 if (evacuation_failed()) {
3836 _summary_bytes_used = recalculate_used();
3837 } else {
3838 // The "used" of the the collection set have already been subtracted
3839 // when they were freed. Add in the bytes evacuated.
3840 _summary_bytes_used += g1_policy()->bytes_copied_during_gc();
3841 }
3842
3843 if (g1_policy()->during_initial_mark_pause()) {
3844 // We have to do this before we notify the CM threads that
3845 // they can start working to make sure that all the
3846 // appropriate initialization is done on the CM object.
3847 concurrent_mark()->checkpointRootsInitialPost();
3848 set_marking_started();
3849 // Note that we don't actually trigger the CM thread at
3850 // this point. We do that later when we're sure that
3851 // the current thread has completed its logging output.
3852 }
3853
3854 allocate_dummy_regions();
3855
3856 #if YOUNG_LIST_VERBOSE
3857 gclog_or_tty->print_cr("\nEnd of the pause.\nYoung_list:");
3858 _young_list->print();
3859 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
3860 #endif // YOUNG_LIST_VERBOSE
3861
3862 init_mutator_alloc_region();
3863
3864 {
3865 size_t expand_bytes = g1_policy()->expansion_amount();
3866 if (expand_bytes > 0) {
3867 size_t bytes_before = capacity();
3868 // No need for an ergo verbose message here,
3869 // expansion_amount() does this when it returns a value > 0.
3870 if (!expand(expand_bytes)) {
3871 // We failed to expand the heap so let's verify that
3872 // committed/uncommitted amount match the backing store
3873 assert(capacity() == _g1_storage.committed_size(), "committed size mismatch");
3874 assert(max_capacity() == _g1_storage.reserved_size(), "reserved size mismatch");
3875 }
3876 }
3877 }
3878
3879 // We redo the verificaiton but now wrt to the new CSet which
3880 // has just got initialized after the previous CSet was freed.
3881 _cm->verify_no_cset_oops(true /* verify_stacks */,
3882 true /* verify_enqueued_buffers */,
3883 true /* verify_thread_buffers */,
3884 true /* verify_fingers */);
3885 _cm->note_end_of_gc();
3886
3887 // This timing is only used by the ergonomics to handle our pause target.
3888 // It is unclear why this should not include the full pause. We will
3889 // investigate this in CR 7178365.
3890 double sample_end_time_sec = os::elapsedTime();
3891 double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS;
3892 g1_policy()->record_collection_pause_end(pause_time_ms);
3893
3894 MemoryService::track_memory_usage();
3895
3896 // In prepare_for_verify() below we'll need to scan the deferred
3897 // update buffers to bring the RSets up-to-date if
3898 // G1HRRSFlushLogBuffersOnVerify has been set. While scanning
3899 // the update buffers we'll probably need to scan cards on the
3900 // regions we just allocated to (i.e., the GC alloc
3901 // regions). However, during the last GC we called
3902 // set_saved_mark() on all the GC alloc regions, so card
3903 // scanning might skip the [saved_mark_word()...top()] area of
3904 // those regions (i.e., the area we allocated objects into
3905 // during the last GC). But it shouldn't. Given that
3906 // saved_mark_word() is conditional on whether the GC time stamp
3907 // on the region is current or not, by incrementing the GC time
3908 // stamp here we invalidate all the GC time stamps on all the
3909 // regions and saved_mark_word() will simply return top() for
3910 // all the regions. This is a nicer way of ensuring this rather
3911 // than iterating over the regions and fixing them. In fact, the
3912 // GC time stamp increment here also ensures that
3913 // saved_mark_word() will return top() between pauses, i.e.,
3914 // during concurrent refinement. So we don't need the
3915 // is_gc_active() check to decided which top to use when
3916 // scanning cards (see CR 7039627).
3917 increment_gc_time_stamp();
3918
3919 if (VerifyAfterGC && total_collections() >= VerifyGCStartAt) {
3920 HandleMark hm; // Discard invalid handles created during verification
3921 gclog_or_tty->print(" VerifyAfterGC:");
3922 prepare_for_verify();
3923 Universe::verify(/* silent */ false,
3924 /* option */ VerifyOption_G1UsePrevMarking);
3925 }
3926
3927 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
3928 ref_processor_stw()->verify_no_references_recorded();
3929
3930 // CM reference discovery will be re-enabled if necessary.
3931 }
3932
3933 // We should do this after we potentially expand the heap so
3934 // that all the COMMIT events are generated before the end GC
3935 // event, and after we retire the GC alloc regions so that all
3936 // RETIRE events are generated before the end GC event.
3937 _hr_printer.end_gc(false /* full */, (size_t) total_collections());
3938
3939 if (mark_in_progress()) {
3940 concurrent_mark()->update_g1_committed();
3941 }
3942
3943 #ifdef TRACESPINNING
3944 ParallelTaskTerminator::print_termination_counts();
3945 #endif
3946
3947 gc_epilogue(false);
3948
3949 g1_policy()->phase_times()->note_gc_end(os::elapsedTime());
3950
3951 // We have to do this after we decide whether to expand the heap or not.
3952 g1_policy()->print_heap_transition();
3953 }
3954
3955 // It is not yet to safe to tell the concurrent mark to
3956 // start as we have some optional output below. We don't want the
3957 // output from the concurrent mark thread interfering with this
3958 // logging output either.
3959
3960 _hrs.verify_optional();
3961 verify_region_sets_optional();
3962
3963 TASKQUEUE_STATS_ONLY(if (ParallelGCVerbose) print_taskqueue_stats());
3964 TASKQUEUE_STATS_ONLY(reset_taskqueue_stats());
3965
3966 print_heap_after_gc();
3967
3968 // We must call G1MonitoringSupport::update_sizes() in the same scoping level
3969 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
3970 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
3971 // before any GC notifications are raised.
3972 g1mm()->update_sizes();
3973 }
3974
3975 if (G1SummarizeRSetStats &&
3976 (G1SummarizeRSetStatsPeriod > 0) &&
3977 (total_collections() % G1SummarizeRSetStatsPeriod == 0)) {
3978 g1_rem_set()->print_summary_info();
3979 }
3980
3981 // It should now be safe to tell the concurrent mark thread to start
3982 // without its logging output interfering with the logging output
3983 // that came from the pause.
3984
3985 if (should_start_conc_mark) {
3986 // CAUTION: after the doConcurrentMark() call below,
3987 // the concurrent marking thread(s) could be running
3988 // concurrently with us. Make sure that anything after
3989 // this point does not assume that we are the only GC thread
3990 // running. Note: of course, the actual marking work will
3991 // not start until the safepoint itself is released in
3992 // ConcurrentGCThread::safepoint_desynchronize().
3993 doConcurrentMark();
3994 }
3995
3996 return true;
3997 }
3998
3999 size_t G1CollectedHeap::desired_plab_sz(GCAllocPurpose purpose)
4000 {
4001 size_t gclab_word_size;
4002 switch (purpose) {
4003 case GCAllocForSurvived:
4004 gclab_word_size = YoungPLABSize;
4005 break;
4006 case GCAllocForTenured:
4007 gclab_word_size = OldPLABSize;
4008 break;
4009 default:
4010 assert(false, "unknown GCAllocPurpose");
4011 gclab_word_size = OldPLABSize;
4012 break;
4013 }
4014 return gclab_word_size;
4015 }
4016
4017 void G1CollectedHeap::init_mutator_alloc_region() {
4018 assert(_mutator_alloc_region.get() == NULL, "pre-condition");
4019 _mutator_alloc_region.init();
4020 }
4021
4022 void G1CollectedHeap::release_mutator_alloc_region() {
4023 _mutator_alloc_region.release();
4024 assert(_mutator_alloc_region.get() == NULL, "post-condition");
4025 }
4026
4027 void G1CollectedHeap::init_gc_alloc_regions() {
4028 assert_at_safepoint(true /* should_be_vm_thread */);
4029
4030 _survivor_gc_alloc_region.init();
4031 _old_gc_alloc_region.init();
4032 HeapRegion* retained_region = _retained_old_gc_alloc_region;
4033 _retained_old_gc_alloc_region = NULL;
4034
4035 // We will discard the current GC alloc region if:
4036 // a) it's in the collection set (it can happen!),
4037 // b) it's already full (no point in using it),
4038 // c) it's empty (this means that it was emptied during
4039 // a cleanup and it should be on the free list now), or
4040 // d) it's humongous (this means that it was emptied
4041 // during a cleanup and was added to the free list, but
4042 // has been subseqently used to allocate a humongous
4043 // object that may be less than the region size).
4044 if (retained_region != NULL &&
4045 !retained_region->in_collection_set() &&
4046 !(retained_region->top() == retained_region->end()) &&
4047 !retained_region->is_empty() &&
4048 !retained_region->isHumongous()) {
4049 retained_region->set_saved_mark();
4050 // The retained region was added to the old region set when it was
4051 // retired. We have to remove it now, since we don't allow regions
4052 // we allocate to in the region sets. We'll re-add it later, when
4053 // it's retired again.
4054 _old_set.remove(retained_region);
4055 bool during_im = g1_policy()->during_initial_mark_pause();
4056 retained_region->note_start_of_copying(during_im);
4057 _old_gc_alloc_region.set(retained_region);
4058 _hr_printer.reuse(retained_region);
4059 }
4060 }
4061
4062 void G1CollectedHeap::release_gc_alloc_regions() {
4063 _survivor_gc_alloc_region.release();
4064 // If we have an old GC alloc region to release, we'll save it in
4065 // _retained_old_gc_alloc_region. If we don't
4066 // _retained_old_gc_alloc_region will become NULL. This is what we
4067 // want either way so no reason to check explicitly for either
4068 // condition.
4069 _retained_old_gc_alloc_region = _old_gc_alloc_region.release();
4070 }
4071
4072 void G1CollectedHeap::abandon_gc_alloc_regions() {
4073 assert(_survivor_gc_alloc_region.get() == NULL, "pre-condition");
4074 assert(_old_gc_alloc_region.get() == NULL, "pre-condition");
4075 _retained_old_gc_alloc_region = NULL;
4076 }
4077
4078 void G1CollectedHeap::init_for_evac_failure(OopsInHeapRegionClosure* cl) {
4079 _drain_in_progress = false;
4080 set_evac_failure_closure(cl);
4081 _evac_failure_scan_stack = new (ResourceObj::C_HEAP, mtGC) GrowableArray<oop>(40, true);
4082 }
4083
4084 void G1CollectedHeap::finalize_for_evac_failure() {
4085 assert(_evac_failure_scan_stack != NULL &&
4086 _evac_failure_scan_stack->length() == 0,
4087 "Postcondition");
4088 assert(!_drain_in_progress, "Postcondition");
4089 delete _evac_failure_scan_stack;
4090 _evac_failure_scan_stack = NULL;
4091 }
4092
4093 void G1CollectedHeap::remove_self_forwarding_pointers() {
4094 assert(check_cset_heap_region_claim_values(HeapRegion::InitialClaimValue), "sanity");
4095
4096 G1ParRemoveSelfForwardPtrsTask rsfp_task(this);
4097
4098 if (G1CollectedHeap::use_parallel_gc_threads()) {
4099 set_par_threads();
4100 workers()->run_task(&rsfp_task);
4101 set_par_threads(0);
4102 } else {
4103 rsfp_task.work(0);
4104 }
4105
4106 assert(check_cset_heap_region_claim_values(HeapRegion::ParEvacFailureClaimValue), "sanity");
4107
4108 // Reset the claim values in the regions in the collection set.
4109 reset_cset_heap_region_claim_values();
4110
4111 assert(check_cset_heap_region_claim_values(HeapRegion::InitialClaimValue), "sanity");
4112
4113 // Now restore saved marks, if any.
4114 if (_objs_with_preserved_marks != NULL) {
4115 assert(_preserved_marks_of_objs != NULL, "Both or none.");
4116 guarantee(_objs_with_preserved_marks->length() ==
4117 _preserved_marks_of_objs->length(), "Both or none.");
4118 for (int i = 0; i < _objs_with_preserved_marks->length(); i++) {
4119 oop obj = _objs_with_preserved_marks->at(i);
4120 markOop m = _preserved_marks_of_objs->at(i);
4121 obj->set_mark(m);
4122 }
4123
4124 // Delete the preserved marks growable arrays (allocated on the C heap).
4125 delete _objs_with_preserved_marks;
4126 delete _preserved_marks_of_objs;
4127 _objs_with_preserved_marks = NULL;
4128 _preserved_marks_of_objs = NULL;
4129 }
4130 }
4131
4132 void G1CollectedHeap::push_on_evac_failure_scan_stack(oop obj) {
4133 _evac_failure_scan_stack->push(obj);
4134 }
4135
4136 void G1CollectedHeap::drain_evac_failure_scan_stack() {
4137 assert(_evac_failure_scan_stack != NULL, "precondition");
4138
4139 while (_evac_failure_scan_stack->length() > 0) {
4140 oop obj = _evac_failure_scan_stack->pop();
4141 _evac_failure_closure->set_region(heap_region_containing(obj));
4142 obj->oop_iterate_backwards(_evac_failure_closure);
4143 }
4144 }
4145
4146 oop
4147 G1CollectedHeap::handle_evacuation_failure_par(OopsInHeapRegionClosure* cl,
4148 oop old) {
4149 assert(obj_in_cs(old),
4150 err_msg("obj: "PTR_FORMAT" should still be in the CSet",
4151 (HeapWord*) old));
4152 markOop m = old->mark();
4153 oop forward_ptr = old->forward_to_atomic(old);
4154 if (forward_ptr == NULL) {
4155 // Forward-to-self succeeded.
4156
4157 if (_evac_failure_closure != cl) {
4158 MutexLockerEx x(EvacFailureStack_lock, Mutex::_no_safepoint_check_flag);
4159 assert(!_drain_in_progress,
4160 "Should only be true while someone holds the lock.");
4161 // Set the global evac-failure closure to the current thread's.
4162 assert(_evac_failure_closure == NULL, "Or locking has failed.");
4163 set_evac_failure_closure(cl);
4164 // Now do the common part.
4165 handle_evacuation_failure_common(old, m);
4166 // Reset to NULL.
4167 set_evac_failure_closure(NULL);
4168 } else {
4169 // The lock is already held, and this is recursive.
4170 assert(_drain_in_progress, "This should only be the recursive case.");
4171 handle_evacuation_failure_common(old, m);
4172 }
4173 return old;
4174 } else {
4175 // Forward-to-self failed. Either someone else managed to allocate
4176 // space for this object (old != forward_ptr) or they beat us in
4177 // self-forwarding it (old == forward_ptr).
4178 assert(old == forward_ptr || !obj_in_cs(forward_ptr),
4179 err_msg("obj: "PTR_FORMAT" forwarded to: "PTR_FORMAT" "
4180 "should not be in the CSet",
4181 (HeapWord*) old, (HeapWord*) forward_ptr));
4182 return forward_ptr;
4183 }
4184 }
4185
4186 void G1CollectedHeap::handle_evacuation_failure_common(oop old, markOop m) {
4187 set_evacuation_failed(true);
4188
4189 preserve_mark_if_necessary(old, m);
4190
4191 HeapRegion* r = heap_region_containing(old);
4192 if (!r->evacuation_failed()) {
4193 r->set_evacuation_failed(true);
4194 _hr_printer.evac_failure(r);
4195 }
4196
4197 push_on_evac_failure_scan_stack(old);
4198
4199 if (!_drain_in_progress) {
4200 // prevent recursion in copy_to_survivor_space()
4201 _drain_in_progress = true;
4202 drain_evac_failure_scan_stack();
4203 _drain_in_progress = false;
4204 }
4205 }
4206
4207 void G1CollectedHeap::preserve_mark_if_necessary(oop obj, markOop m) {
4208 assert(evacuation_failed(), "Oversaving!");
4209 // We want to call the "for_promotion_failure" version only in the
4210 // case of a promotion failure.
4211 if (m->must_be_preserved_for_promotion_failure(obj)) {
4212 if (_objs_with_preserved_marks == NULL) {
4213 assert(_preserved_marks_of_objs == NULL, "Both or none.");
4214 _objs_with_preserved_marks =
4215 new (ResourceObj::C_HEAP, mtGC) GrowableArray<oop>(40, true);
4216 _preserved_marks_of_objs =
4217 new (ResourceObj::C_HEAP, mtGC) GrowableArray<markOop>(40, true);
4218 }
4219 _objs_with_preserved_marks->push(obj);
4220 _preserved_marks_of_objs->push(m);
4221 }
4222 }
4223
4224 HeapWord* G1CollectedHeap::par_allocate_during_gc(GCAllocPurpose purpose,
4225 size_t word_size) {
4226 if (purpose == GCAllocForSurvived) {
4227 HeapWord* result = survivor_attempt_allocation(word_size);
4228 if (result != NULL) {
4229 return result;
4230 } else {
4231 // Let's try to allocate in the old gen in case we can fit the
4232 // object there.
4233 return old_attempt_allocation(word_size);
4234 }
4235 } else {
4236 assert(purpose == GCAllocForTenured, "sanity");
4237 HeapWord* result = old_attempt_allocation(word_size);
4238 if (result != NULL) {
4239 return result;
4240 } else {
4241 // Let's try to allocate in the survivors in case we can fit the
4242 // object there.
4243 return survivor_attempt_allocation(word_size);
4244 }
4245 }
4246
4247 ShouldNotReachHere();
4248 // Trying to keep some compilers happy.
4249 return NULL;
4250 }
4251
4252 G1ParGCAllocBuffer::G1ParGCAllocBuffer(size_t gclab_word_size) :
4253 ParGCAllocBuffer(gclab_word_size), _retired(false) { }
4254
4255 G1ParScanThreadState::G1ParScanThreadState(G1CollectedHeap* g1h, uint queue_num)
4256 : _g1h(g1h),
4257 _refs(g1h->task_queue(queue_num)),
4258 _dcq(&g1h->dirty_card_queue_set()),
4259 _ct_bs((CardTableModRefBS*)_g1h->barrier_set()),
4260 _g1_rem(g1h->g1_rem_set()),
4261 _hash_seed(17), _queue_num(queue_num),
4262 _term_attempts(0),
4263 _surviving_alloc_buffer(g1h->desired_plab_sz(GCAllocForSurvived)),
4264 _tenured_alloc_buffer(g1h->desired_plab_sz(GCAllocForTenured)),
4265 _age_table(false),
4266 _strong_roots_time(0), _term_time(0),
4267 _alloc_buffer_waste(0), _undo_waste(0) {
4268 // we allocate G1YoungSurvRateNumRegions plus one entries, since
4269 // we "sacrifice" entry 0 to keep track of surviving bytes for
4270 // non-young regions (where the age is -1)
4271 // We also add a few elements at the beginning and at the end in
4272 // an attempt to eliminate cache contention
4273 uint real_length = 1 + _g1h->g1_policy()->young_cset_region_length();
4274 uint array_length = PADDING_ELEM_NUM +
4275 real_length +
4276 PADDING_ELEM_NUM;
4277 _surviving_young_words_base = NEW_C_HEAP_ARRAY(size_t, array_length, mtGC);
4278 if (_surviving_young_words_base == NULL)
4279 vm_exit_out_of_memory(array_length * sizeof(size_t),
4280 "Not enough space for young surv histo.");
4281 _surviving_young_words = _surviving_young_words_base + PADDING_ELEM_NUM;
4282 memset(_surviving_young_words, 0, (size_t) real_length * sizeof(size_t));
4283
4284 _alloc_buffers[GCAllocForSurvived] = &_surviving_alloc_buffer;
4285 _alloc_buffers[GCAllocForTenured] = &_tenured_alloc_buffer;
4286
4287 _start = os::elapsedTime();
4288 }
4289
4290 void
4291 G1ParScanThreadState::print_termination_stats_hdr(outputStream* const st)
4292 {
4293 st->print_raw_cr("GC Termination Stats");
4294 st->print_raw_cr(" elapsed --strong roots-- -------termination-------"
4295 " ------waste (KiB)------");
4296 st->print_raw_cr("thr ms ms % ms % attempts"
4297 " total alloc undo");
4298 st->print_raw_cr("--- --------- --------- ------ --------- ------ --------"
4299 " ------- ------- -------");
4300 }
4301
4302 void
4303 G1ParScanThreadState::print_termination_stats(int i,
4304 outputStream* const st) const
4305 {
4306 const double elapsed_ms = elapsed_time() * 1000.0;
4307 const double s_roots_ms = strong_roots_time() * 1000.0;
4308 const double term_ms = term_time() * 1000.0;
4309 st->print_cr("%3d %9.2f %9.2f %6.2f "
4310 "%9.2f %6.2f " SIZE_FORMAT_W(8) " "
4311 SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7),
4312 i, elapsed_ms, s_roots_ms, s_roots_ms * 100 / elapsed_ms,
4313 term_ms, term_ms * 100 / elapsed_ms, term_attempts(),
4314 (alloc_buffer_waste() + undo_waste()) * HeapWordSize / K,
4315 alloc_buffer_waste() * HeapWordSize / K,
4316 undo_waste() * HeapWordSize / K);
4317 }
4318
4319 #ifdef ASSERT
4320 bool G1ParScanThreadState::verify_ref(narrowOop* ref) const {
4321 assert(ref != NULL, "invariant");
4322 assert(UseCompressedOops, "sanity");
4323 assert(!has_partial_array_mask(ref), err_msg("ref=" PTR_FORMAT, ref));
4324 oop p = oopDesc::load_decode_heap_oop(ref);
4325 assert(_g1h->is_in_g1_reserved(p),
4326 err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, intptr_t(p)));
4327 return true;
4328 }
4329
4330 bool G1ParScanThreadState::verify_ref(oop* ref) const {
4331 assert(ref != NULL, "invariant");
4332 if (has_partial_array_mask(ref)) {
4333 // Must be in the collection set--it's already been copied.
4334 oop p = clear_partial_array_mask(ref);
4335 assert(_g1h->obj_in_cs(p),
4336 err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, intptr_t(p)));
4337 } else {
4338 oop p = oopDesc::load_decode_heap_oop(ref);
4339 assert(_g1h->is_in_g1_reserved(p),
4340 err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, intptr_t(p)));
4341 }
4342 return true;
4343 }
4344
4345 bool G1ParScanThreadState::verify_task(StarTask ref) const {
4346 if (ref.is_narrow()) {
4347 return verify_ref((narrowOop*) ref);
4348 } else {
4349 return verify_ref((oop*) ref);
4350 }
4351 }
4352 #endif // ASSERT
4353
4354 void G1ParScanThreadState::trim_queue() {
4355 assert(_evac_cl != NULL, "not set");
4356 assert(_evac_failure_cl != NULL, "not set");
4357 assert(_partial_scan_cl != NULL, "not set");
4358
4359 StarTask ref;
4360 do {
4361 // Drain the overflow stack first, so other threads can steal.
4362 while (refs()->pop_overflow(ref)) {
4363 deal_with_reference(ref);
4364 }
4365
4366 while (refs()->pop_local(ref)) {
4367 deal_with_reference(ref);
4368 }
4369 } while (!refs()->is_empty());
4370 }
4371
4372 G1ParClosureSuper::G1ParClosureSuper(G1CollectedHeap* g1,
4373 G1ParScanThreadState* par_scan_state) :
4374 _g1(g1), _g1_rem(_g1->g1_rem_set()), _cm(_g1->concurrent_mark()),
4375 _par_scan_state(par_scan_state),
4376 _worker_id(par_scan_state->queue_num()),
4377 _during_initial_mark(_g1->g1_policy()->during_initial_mark_pause()),
4378 _mark_in_progress(_g1->mark_in_progress()) { }
4379
4380 template <bool do_gen_barrier, G1Barrier barrier, bool do_mark_object>
4381 void G1ParCopyClosure<do_gen_barrier, barrier, do_mark_object>::mark_object(oop obj) {
4382 #ifdef ASSERT
4383 HeapRegion* hr = _g1->heap_region_containing(obj);
4384 assert(hr != NULL, "sanity");
4385 assert(!hr->in_collection_set(), "should not mark objects in the CSet");
4386 #endif // ASSERT
4387
4388 // We know that the object is not moving so it's safe to read its size.
4389 _cm->grayRoot(obj, (size_t) obj->size(), _worker_id);
4390 }
4391
4392 template <bool do_gen_barrier, G1Barrier barrier, bool do_mark_object>
4393 void G1ParCopyClosure<do_gen_barrier, barrier, do_mark_object>
4394 ::mark_forwarded_object(oop from_obj, oop to_obj) {
4395 #ifdef ASSERT
4396 assert(from_obj->is_forwarded(), "from obj should be forwarded");
4397 assert(from_obj->forwardee() == to_obj, "to obj should be the forwardee");
4398 assert(from_obj != to_obj, "should not be self-forwarded");
4399
4400 HeapRegion* from_hr = _g1->heap_region_containing(from_obj);
4401 assert(from_hr != NULL, "sanity");
4402 assert(from_hr->in_collection_set(), "from obj should be in the CSet");
4403
4404 HeapRegion* to_hr = _g1->heap_region_containing(to_obj);
4405 assert(to_hr != NULL, "sanity");
4406 assert(!to_hr->in_collection_set(), "should not mark objects in the CSet");
4407 #endif // ASSERT
4408
4409 // The object might be in the process of being copied by another
4410 // worker so we cannot trust that its to-space image is
4411 // well-formed. So we have to read its size from its from-space
4412 // image which we know should not be changing.
4413 _cm->grayRoot(to_obj, (size_t) from_obj->size(), _worker_id);
4414 }
4415
4416 template <bool do_gen_barrier, G1Barrier barrier, bool do_mark_object>
4417 oop G1ParCopyClosure<do_gen_barrier, barrier, do_mark_object>
4418 ::copy_to_survivor_space(oop old) {
4419 size_t word_sz = old->size();
4420 HeapRegion* from_region = _g1->heap_region_containing_raw(old);
4421 // +1 to make the -1 indexes valid...
4422 int young_index = from_region->young_index_in_cset()+1;
4423 assert( (from_region->is_young() && young_index > 0) ||
4424 (!from_region->is_young() && young_index == 0), "invariant" );
4425 G1CollectorPolicy* g1p = _g1->g1_policy();
4426 markOop m = old->mark();
4427 int age = m->has_displaced_mark_helper() ? m->displaced_mark_helper()->age()
4428 : m->age();
4429 GCAllocPurpose alloc_purpose = g1p->evacuation_destination(from_region, age,
4430 word_sz);
4431 HeapWord* obj_ptr = _par_scan_state->allocate(alloc_purpose, word_sz);
4432 oop obj = oop(obj_ptr);
4433
4434 if (obj_ptr == NULL) {
4435 // This will either forward-to-self, or detect that someone else has
4436 // installed a forwarding pointer.
4437 OopsInHeapRegionClosure* cl = _par_scan_state->evac_failure_closure();
4438 return _g1->handle_evacuation_failure_par(cl, old);
4439 }
4440
4441 // We're going to allocate linearly, so might as well prefetch ahead.
4442 Prefetch::write(obj_ptr, PrefetchCopyIntervalInBytes);
4443
4444 oop forward_ptr = old->forward_to_atomic(obj);
4445 if (forward_ptr == NULL) {
4446 Copy::aligned_disjoint_words((HeapWord*) old, obj_ptr, word_sz);
4447 if (g1p->track_object_age(alloc_purpose)) {
4448 // We could simply do obj->incr_age(). However, this causes a
4449 // performance issue. obj->incr_age() will first check whether
4450 // the object has a displaced mark by checking its mark word;
4451 // getting the mark word from the new location of the object
4452 // stalls. So, given that we already have the mark word and we
4453 // are about to install it anyway, it's better to increase the
4454 // age on the mark word, when the object does not have a
4455 // displaced mark word. We're not expecting many objects to have
4456 // a displaced marked word, so that case is not optimized
4457 // further (it could be...) and we simply call obj->incr_age().
4458
4459 if (m->has_displaced_mark_helper()) {
4460 // in this case, we have to install the mark word first,
4461 // otherwise obj looks to be forwarded (the old mark word,
4462 // which contains the forward pointer, was copied)
4463 obj->set_mark(m);
4464 obj->incr_age();
4465 } else {
4466 m = m->incr_age();
4467 obj->set_mark(m);
4468 }
4469 _par_scan_state->age_table()->add(obj, word_sz);
4470 } else {
4471 obj->set_mark(m);
4472 }
4473
4474 size_t* surv_young_words = _par_scan_state->surviving_young_words();
4475 surv_young_words[young_index] += word_sz;
4476
4477 if (obj->is_objArray() && arrayOop(obj)->length() >= ParGCArrayScanChunk) {
4478 // We keep track of the next start index in the length field of
4479 // the to-space object. The actual length can be found in the
4480 // length field of the from-space object.
4481 arrayOop(obj)->set_length(0);
4482 oop* old_p = set_partial_array_mask(old);
4483 _par_scan_state->push_on_queue(old_p);
4484 } else {
4485 // No point in using the slower heap_region_containing() method,
4486 // given that we know obj is in the heap.
4487 _scanner.set_region(_g1->heap_region_containing_raw(obj));
4488 obj->oop_iterate_backwards(&_scanner);
4489 }
4490 } else {
4491 _par_scan_state->undo_allocation(alloc_purpose, obj_ptr, word_sz);
4492 obj = forward_ptr;
4493 }
4494 return obj;
4495 }
4496
4497 template <bool do_gen_barrier, G1Barrier barrier, bool do_mark_object>
4498 template <class T>
4499 void G1ParCopyClosure<do_gen_barrier, barrier, do_mark_object>
4500 ::do_oop_work(T* p) {
4501 oop obj = oopDesc::load_decode_heap_oop(p);
4502 assert(barrier != G1BarrierRS || obj != NULL,
4503 "Precondition: G1BarrierRS implies obj is non-NULL");
4504
4505 assert(_worker_id == _par_scan_state->queue_num(), "sanity");
4506
4507 // here the null check is implicit in the cset_fast_test() test
4508 if (_g1->in_cset_fast_test(obj)) {
4509 oop forwardee;
4510 if (obj->is_forwarded()) {
4511 forwardee = obj->forwardee();
4512 } else {
4513 forwardee = copy_to_survivor_space(obj);
4514 }
4515 assert(forwardee != NULL, "forwardee should not be NULL");
4516 oopDesc::encode_store_heap_oop(p, forwardee);
4517 if (do_mark_object && forwardee != obj) {
4518 // If the object is self-forwarded we don't need to explicitly
4519 // mark it, the evacuation failure protocol will do so.
4520 mark_forwarded_object(obj, forwardee);
4521 }
4522
4523 // When scanning the RS, we only care about objs in CS.
4524 if (barrier == G1BarrierRS) {
4525 _par_scan_state->update_rs(_from, p, _worker_id);
4526 }
4527 } else {
4528 // The object is not in collection set. If we're a root scanning
4529 // closure during an initial mark pause (i.e. do_mark_object will
4530 // be true) then attempt to mark the object.
4531 if (do_mark_object && _g1->is_in_g1_reserved(obj)) {
4532 mark_object(obj);
4533 }
4534 }
4535
4536 if (barrier == G1BarrierEvac && obj != NULL) {
4537 _par_scan_state->update_rs(_from, p, _worker_id);
4538 }
4539
4540 if (do_gen_barrier && obj != NULL) {
4541 par_do_barrier(p);
4542 }
4543 }
4544
4545 template void G1ParCopyClosure<false, G1BarrierEvac, false>::do_oop_work(oop* p);
4546 template void G1ParCopyClosure<false, G1BarrierEvac, false>::do_oop_work(narrowOop* p);
4547
4548 template <class T> void G1ParScanPartialArrayClosure::do_oop_nv(T* p) {
4549 assert(has_partial_array_mask(p), "invariant");
4550 oop from_obj = clear_partial_array_mask(p);
4551
4552 assert(Universe::heap()->is_in_reserved(from_obj), "must be in heap.");
4553 assert(from_obj->is_objArray(), "must be obj array");
4554 objArrayOop from_obj_array = objArrayOop(from_obj);
4555 // The from-space object contains the real length.
4556 int length = from_obj_array->length();
4557
4558 assert(from_obj->is_forwarded(), "must be forwarded");
4559 oop to_obj = from_obj->forwardee();
4560 assert(from_obj != to_obj, "should not be chunking self-forwarded objects");
4561 objArrayOop to_obj_array = objArrayOop(to_obj);
4562 // We keep track of the next start index in the length field of the
4563 // to-space object.
4564 int next_index = to_obj_array->length();
4565 assert(0 <= next_index && next_index < length,
4566 err_msg("invariant, next index: %d, length: %d", next_index, length));
4567
4568 int start = next_index;
4569 int end = length;
4570 int remainder = end - start;
4571 // We'll try not to push a range that's smaller than ParGCArrayScanChunk.
4572 if (remainder > 2 * ParGCArrayScanChunk) {
4573 end = start + ParGCArrayScanChunk;
4574 to_obj_array->set_length(end);
4575 // Push the remainder before we process the range in case another
4576 // worker has run out of things to do and can steal it.
4577 oop* from_obj_p = set_partial_array_mask(from_obj);
4578 _par_scan_state->push_on_queue(from_obj_p);
4579 } else {
4580 assert(length == end, "sanity");
4581 // We'll process the final range for this object. Restore the length
4582 // so that the heap remains parsable in case of evacuation failure.
4583 to_obj_array->set_length(end);
4584 }
4585 _scanner.set_region(_g1->heap_region_containing_raw(to_obj));
4586 // Process indexes [start,end). It will also process the header
4587 // along with the first chunk (i.e., the chunk with start == 0).
4588 // Note that at this point the length field of to_obj_array is not
4589 // correct given that we are using it to keep track of the next
4590 // start index. oop_iterate_range() (thankfully!) ignores the length
4591 // field and only relies on the start / end parameters. It does
4592 // however return the size of the object which will be incorrect. So
4593 // we have to ignore it even if we wanted to use it.
4594 to_obj_array->oop_iterate_range(&_scanner, start, end);
4595 }
4596
4597 class G1ParEvacuateFollowersClosure : public VoidClosure {
4598 protected:
4599 G1CollectedHeap* _g1h;
4600 G1ParScanThreadState* _par_scan_state;
4601 RefToScanQueueSet* _queues;
4602 ParallelTaskTerminator* _terminator;
4603
4604 G1ParScanThreadState* par_scan_state() { return _par_scan_state; }
4605 RefToScanQueueSet* queues() { return _queues; }
4606 ParallelTaskTerminator* terminator() { return _terminator; }
4607
4608 public:
4609 G1ParEvacuateFollowersClosure(G1CollectedHeap* g1h,
4610 G1ParScanThreadState* par_scan_state,
4611 RefToScanQueueSet* queues,
4612 ParallelTaskTerminator* terminator)
4613 : _g1h(g1h), _par_scan_state(par_scan_state),
4614 _queues(queues), _terminator(terminator) {}
4615
4616 void do_void();
4617
4618 private:
4619 inline bool offer_termination();
4620 };
4621
4622 bool G1ParEvacuateFollowersClosure::offer_termination() {
4623 G1ParScanThreadState* const pss = par_scan_state();
4624 pss->start_term_time();
4625 const bool res = terminator()->offer_termination();
4626 pss->end_term_time();
4627 return res;
4628 }
4629
4630 void G1ParEvacuateFollowersClosure::do_void() {
4631 StarTask stolen_task;
4632 G1ParScanThreadState* const pss = par_scan_state();
4633 pss->trim_queue();
4634
4635 do {
4636 while (queues()->steal(pss->queue_num(), pss->hash_seed(), stolen_task)) {
4637 assert(pss->verify_task(stolen_task), "sanity");
4638 if (stolen_task.is_narrow()) {
4639 pss->deal_with_reference((narrowOop*) stolen_task);
4640 } else {
4641 pss->deal_with_reference((oop*) stolen_task);
4642 }
4643
4644 // We've just processed a reference and we might have made
4645 // available new entries on the queues. So we have to make sure
4646 // we drain the queues as necessary.
4647 pss->trim_queue();
4648 }
4649 } while (!offer_termination());
4650
4651 pss->retire_alloc_buffers();
4652 }
4653
4654 class G1ParTask : public AbstractGangTask {
4655 protected:
4656 G1CollectedHeap* _g1h;
4657 RefToScanQueueSet *_queues;
4658 ParallelTaskTerminator _terminator;
4659 uint _n_workers;
4660
4661 Mutex _stats_lock;
4662 Mutex* stats_lock() { return &_stats_lock; }
4663
4664 size_t getNCards() {
4665 return (_g1h->capacity() + G1BlockOffsetSharedArray::N_bytes - 1)
4666 / G1BlockOffsetSharedArray::N_bytes;
4667 }
4668
4669 public:
4670 G1ParTask(G1CollectedHeap* g1h,
4671 RefToScanQueueSet *task_queues)
4672 : AbstractGangTask("G1 collection"),
4673 _g1h(g1h),
4674 _queues(task_queues),
4675 _terminator(0, _queues),
4676 _stats_lock(Mutex::leaf, "parallel G1 stats lock", true)
4677 {}
4678
4679 RefToScanQueueSet* queues() { return _queues; }
4680
4681 RefToScanQueue *work_queue(int i) {
4682 return queues()->queue(i);
4683 }
4684
4685 ParallelTaskTerminator* terminator() { return &_terminator; }
4686
4687 virtual void set_for_termination(int active_workers) {
4688 // This task calls set_n_termination() in par_non_clean_card_iterate_work()
4689 // in the young space (_par_seq_tasks) in the G1 heap
4690 // for SequentialSubTasksDone.
4691 // This task also uses SubTasksDone in SharedHeap and G1CollectedHeap
4692 // both of which need setting by set_n_termination().
4693 _g1h->SharedHeap::set_n_termination(active_workers);
4694 _g1h->set_n_termination(active_workers);
4695 terminator()->reset_for_reuse(active_workers);
4696 _n_workers = active_workers;
4697 }
4698
4699 void work(uint worker_id) {
4700 if (worker_id >= _n_workers) return; // no work needed this round
4701
4702 double start_time_ms = os::elapsedTime() * 1000.0;
4703 _g1h->g1_policy()->phase_times()->record_gc_worker_start_time(worker_id, start_time_ms);
4704
4705 {
4706 ResourceMark rm;
4707 HandleMark hm;
4708
4709 ReferenceProcessor* rp = _g1h->ref_processor_stw();
4710
4711 G1ParScanThreadState pss(_g1h, worker_id);
4712 G1ParScanHeapEvacClosure scan_evac_cl(_g1h, &pss, rp);
4713 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, rp);
4714 G1ParScanPartialArrayClosure partial_scan_cl(_g1h, &pss, rp);
4715
4716 pss.set_evac_closure(&scan_evac_cl);
4717 pss.set_evac_failure_closure(&evac_failure_cl);
4718 pss.set_partial_scan_closure(&partial_scan_cl);
4719
4720 G1ParScanExtRootClosure only_scan_root_cl(_g1h, &pss, rp);
4721 G1ParScanPermClosure only_scan_perm_cl(_g1h, &pss, rp);
4722
4723 G1ParScanAndMarkExtRootClosure scan_mark_root_cl(_g1h, &pss, rp);
4724 G1ParScanAndMarkPermClosure scan_mark_perm_cl(_g1h, &pss, rp);
4725
4726 OopClosure* scan_root_cl = &only_scan_root_cl;
4727 OopsInHeapRegionClosure* scan_perm_cl = &only_scan_perm_cl;
4728
4729 if (_g1h->g1_policy()->during_initial_mark_pause()) {
4730 // We also need to mark copied objects.
4731 scan_root_cl = &scan_mark_root_cl;
4732 scan_perm_cl = &scan_mark_perm_cl;
4733 }
4734
4735 G1ParPushHeapRSClosure push_heap_rs_cl(_g1h, &pss);
4736
4737 pss.start_strong_roots();
4738 _g1h->g1_process_strong_roots(/* not collecting perm */ false,
4739 SharedHeap::SO_AllClasses,
4740 scan_root_cl,
4741 &push_heap_rs_cl,
4742 scan_perm_cl,
4743 worker_id);
4744 pss.end_strong_roots();
4745
4746 {
4747 double start = os::elapsedTime();
4748 G1ParEvacuateFollowersClosure evac(_g1h, &pss, _queues, &_terminator);
4749 evac.do_void();
4750 double elapsed_ms = (os::elapsedTime()-start)*1000.0;
4751 double term_ms = pss.term_time()*1000.0;
4752 _g1h->g1_policy()->phase_times()->add_obj_copy_time(worker_id, elapsed_ms-term_ms);
4753 _g1h->g1_policy()->phase_times()->record_termination(worker_id, term_ms, pss.term_attempts());
4754 }
4755 _g1h->g1_policy()->record_thread_age_table(pss.age_table());
4756 _g1h->update_surviving_young_words(pss.surviving_young_words()+1);
4757
4758 if (ParallelGCVerbose) {
4759 MutexLocker x(stats_lock());
4760 pss.print_termination_stats(worker_id);
4761 }
4762
4763 assert(pss.refs()->is_empty(), "should be empty");
4764
4765 // Close the inner scope so that the ResourceMark and HandleMark
4766 // destructors are executed here and are included as part of the
4767 // "GC Worker Time".
4768 }
4769
4770 double end_time_ms = os::elapsedTime() * 1000.0;
4771 _g1h->g1_policy()->phase_times()->record_gc_worker_end_time(worker_id, end_time_ms);
4772 }
4773 };
4774
4775 // *** Common G1 Evacuation Stuff
4776
4777 // Closures that support the filtering of CodeBlobs scanned during
4778 // external root scanning.
4779
4780 // Closure applied to reference fields in code blobs (specifically nmethods)
4781 // to determine whether an nmethod contains references that point into
4782 // the collection set. Used as a predicate when walking code roots so
4783 // that only nmethods that point into the collection set are added to the
4784 // 'marked' list.
4785
4786 class G1FilteredCodeBlobToOopClosure : public CodeBlobToOopClosure {
4787
4788 class G1PointsIntoCSOopClosure : public OopClosure {
4789 G1CollectedHeap* _g1;
4790 bool _points_into_cs;
4791 public:
4792 G1PointsIntoCSOopClosure(G1CollectedHeap* g1) :
4793 _g1(g1), _points_into_cs(false) { }
4794
4795 bool points_into_cs() const { return _points_into_cs; }
4796
4797 template <class T>
4798 void do_oop_nv(T* p) {
4799 if (!_points_into_cs) {
4800 T heap_oop = oopDesc::load_heap_oop(p);
4801 if (!oopDesc::is_null(heap_oop) &&
4802 _g1->in_cset_fast_test(oopDesc::decode_heap_oop_not_null(heap_oop))) {
4803 _points_into_cs = true;
4804 }
4805 }
4806 }
4807
4808 virtual void do_oop(oop* p) { do_oop_nv(p); }
4809 virtual void do_oop(narrowOop* p) { do_oop_nv(p); }
4810 };
4811
4812 G1CollectedHeap* _g1;
4813
4814 public:
4815 G1FilteredCodeBlobToOopClosure(G1CollectedHeap* g1, OopClosure* cl) :
4816 CodeBlobToOopClosure(cl, true), _g1(g1) { }
4817
4818 virtual void do_code_blob(CodeBlob* cb) {
4819 nmethod* nm = cb->as_nmethod_or_null();
4820 if (nm != NULL && !(nm->test_oops_do_mark())) {
4821 G1PointsIntoCSOopClosure predicate_cl(_g1);
4822 nm->oops_do(&predicate_cl);
4823
4824 if (predicate_cl.points_into_cs()) {
4825 // At least one of the reference fields or the oop relocations
4826 // in the nmethod points into the collection set. We have to
4827 // 'mark' this nmethod.
4828 // Note: Revisit the following if CodeBlobToOopClosure::do_code_blob()
4829 // or MarkingCodeBlobClosure::do_code_blob() change.
4830 if (!nm->test_set_oops_do_mark()) {
4831 do_newly_marked_nmethod(nm);
4832 }
4833 }
4834 }
4835 }
4836 };
4837
4838 // This method is run in a GC worker.
4839
4840 void
4841 G1CollectedHeap::
4842 g1_process_strong_roots(bool collecting_perm_gen,
4843 ScanningOption so,
4844 OopClosure* scan_non_heap_roots,
4845 OopsInHeapRegionClosure* scan_rs,
4846 OopsInGenClosure* scan_perm,
4847 int worker_i) {
4848
4849 // First scan the strong roots, including the perm gen.
4850 double ext_roots_start = os::elapsedTime();
4851 double closure_app_time_sec = 0.0;
4852
4853 BufferingOopClosure buf_scan_non_heap_roots(scan_non_heap_roots);
4854 BufferingOopsInGenClosure buf_scan_perm(scan_perm);
4855 buf_scan_perm.set_generation(perm_gen());
4856
4857 // Walk the code cache w/o buffering, because StarTask cannot handle
4858 // unaligned oop locations.
4859 G1FilteredCodeBlobToOopClosure eager_scan_code_roots(this, scan_non_heap_roots);
4860
4861 process_strong_roots(false, // no scoping; this is parallel code
4862 collecting_perm_gen, so,
4863 &buf_scan_non_heap_roots,
4864 &eager_scan_code_roots,
4865 &buf_scan_perm);
4866
4867 // Now the CM ref_processor roots.
4868 if (!_process_strong_tasks->is_task_claimed(G1H_PS_refProcessor_oops_do)) {
4869 // We need to treat the discovered reference lists of the
4870 // concurrent mark ref processor as roots and keep entries
4871 // (which are added by the marking threads) on them live
4872 // until they can be processed at the end of marking.
4873 ref_processor_cm()->weak_oops_do(&buf_scan_non_heap_roots);
4874 }
4875
4876 // Finish up any enqueued closure apps (attributed as object copy time).
4877 buf_scan_non_heap_roots.done();
4878 buf_scan_perm.done();
4879
4880 double obj_copy_time_sec = buf_scan_perm.closure_app_seconds() +
4881 buf_scan_non_heap_roots.closure_app_seconds();
4882 g1_policy()->phase_times()->record_obj_copy_time(worker_i, obj_copy_time_sec * 1000.0);
4883
4884 double ext_root_time_ms =
4885 ((os::elapsedTime() - ext_roots_start) - obj_copy_time_sec) * 1000.0;
4886
4887 g1_policy()->phase_times()->record_ext_root_scan_time(worker_i, ext_root_time_ms);
4888
4889 // During conc marking we have to filter the per-thread SATB buffers
4890 // to make sure we remove any oops into the CSet (which will show up
4891 // as implicitly live).
4892 double satb_filtering_ms = 0.0;
4893 if (!_process_strong_tasks->is_task_claimed(G1H_PS_filter_satb_buffers)) {
4894 if (mark_in_progress()) {
4895 double satb_filter_start = os::elapsedTime();
4896
4897 JavaThread::satb_mark_queue_set().filter_thread_buffers();
4898
4899 satb_filtering_ms = (os::elapsedTime() - satb_filter_start) * 1000.0;
4900 }
4901 }
4902 g1_policy()->phase_times()->record_satb_filtering_time(worker_i, satb_filtering_ms);
4903
4904 // Now scan the complement of the collection set.
4905 if (scan_rs != NULL) {
4906 g1_rem_set()->oops_into_collection_set_do(scan_rs, worker_i);
4907 }
4908
4909 _process_strong_tasks->all_tasks_completed();
4910 }
4911
4912 void
4913 G1CollectedHeap::g1_process_weak_roots(OopClosure* root_closure,
4914 OopClosure* non_root_closure) {
4915 CodeBlobToOopClosure roots_in_blobs(root_closure, /*do_marking=*/ false);
4916 SharedHeap::process_weak_roots(root_closure, &roots_in_blobs, non_root_closure);
4917 }
4918
4919 // Weak Reference Processing support
4920
4921 // An always "is_alive" closure that is used to preserve referents.
4922 // If the object is non-null then it's alive. Used in the preservation
4923 // of referent objects that are pointed to by reference objects
4924 // discovered by the CM ref processor.
4925 class G1AlwaysAliveClosure: public BoolObjectClosure {
4926 G1CollectedHeap* _g1;
4927 public:
4928 G1AlwaysAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
4929 void do_object(oop p) { assert(false, "Do not call."); }
4930 bool do_object_b(oop p) {
4931 if (p != NULL) {
4932 return true;
4933 }
4934 return false;
4935 }
4936 };
4937
4938 bool G1STWIsAliveClosure::do_object_b(oop p) {
4939 // An object is reachable if it is outside the collection set,
4940 // or is inside and copied.
4941 return !_g1->obj_in_cs(p) || p->is_forwarded();
4942 }
4943
4944 // Non Copying Keep Alive closure
4945 class G1KeepAliveClosure: public OopClosure {
4946 G1CollectedHeap* _g1;
4947 public:
4948 G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
4949 void do_oop(narrowOop* p) { guarantee(false, "Not needed"); }
4950 void do_oop( oop* p) {
4951 oop obj = *p;
4952
4953 if (_g1->obj_in_cs(obj)) {
4954 assert( obj->is_forwarded(), "invariant" );
4955 *p = obj->forwardee();
4956 }
4957 }
4958 };
4959
4960 // Copying Keep Alive closure - can be called from both
4961 // serial and parallel code as long as different worker
4962 // threads utilize different G1ParScanThreadState instances
4963 // and different queues.
4964
4965 class G1CopyingKeepAliveClosure: public OopClosure {
4966 G1CollectedHeap* _g1h;
4967 OopClosure* _copy_non_heap_obj_cl;
4968 OopsInHeapRegionClosure* _copy_perm_obj_cl;
4969 G1ParScanThreadState* _par_scan_state;
4970
4971 public:
4972 G1CopyingKeepAliveClosure(G1CollectedHeap* g1h,
4973 OopClosure* non_heap_obj_cl,
4974 OopsInHeapRegionClosure* perm_obj_cl,
4975 G1ParScanThreadState* pss):
4976 _g1h(g1h),
4977 _copy_non_heap_obj_cl(non_heap_obj_cl),
4978 _copy_perm_obj_cl(perm_obj_cl),
4979 _par_scan_state(pss)
4980 {}
4981
4982 virtual void do_oop(narrowOop* p) { do_oop_work(p); }
4983 virtual void do_oop( oop* p) { do_oop_work(p); }
4984
4985 template <class T> void do_oop_work(T* p) {
4986 oop obj = oopDesc::load_decode_heap_oop(p);
4987
4988 if (_g1h->obj_in_cs(obj)) {
4989 // If the referent object has been forwarded (either copied
4990 // to a new location or to itself in the event of an
4991 // evacuation failure) then we need to update the reference
4992 // field and, if both reference and referent are in the G1
4993 // heap, update the RSet for the referent.
4994 //
4995 // If the referent has not been forwarded then we have to keep
4996 // it alive by policy. Therefore we have copy the referent.
4997 //
4998 // If the reference field is in the G1 heap then we can push
4999 // on the PSS queue. When the queue is drained (after each
5000 // phase of reference processing) the object and it's followers
5001 // will be copied, the reference field set to point to the
5002 // new location, and the RSet updated. Otherwise we need to
5003 // use the the non-heap or perm closures directly to copy
5004 // the refernt object and update the pointer, while avoiding
5005 // updating the RSet.
5006
5007 if (_g1h->is_in_g1_reserved(p)) {
5008 _par_scan_state->push_on_queue(p);
5009 } else {
5010 // The reference field is not in the G1 heap.
5011 if (_g1h->perm_gen()->is_in(p)) {
5012 _copy_perm_obj_cl->do_oop(p);
5013 } else {
5014 _copy_non_heap_obj_cl->do_oop(p);
5015 }
5016 }
5017 }
5018 }
5019 };
5020
5021 // Serial drain queue closure. Called as the 'complete_gc'
5022 // closure for each discovered list in some of the
5023 // reference processing phases.
5024
5025 class G1STWDrainQueueClosure: public VoidClosure {
5026 protected:
5027 G1CollectedHeap* _g1h;
5028 G1ParScanThreadState* _par_scan_state;
5029
5030 G1ParScanThreadState* par_scan_state() { return _par_scan_state; }
5031
5032 public:
5033 G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) :
5034 _g1h(g1h),
5035 _par_scan_state(pss)
5036 { }
5037
5038 void do_void() {
5039 G1ParScanThreadState* const pss = par_scan_state();
5040 pss->trim_queue();
5041 }
5042 };
5043
5044 // Parallel Reference Processing closures
5045
5046 // Implementation of AbstractRefProcTaskExecutor for parallel reference
5047 // processing during G1 evacuation pauses.
5048
5049 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
5050 private:
5051 G1CollectedHeap* _g1h;
5052 RefToScanQueueSet* _queues;
5053 FlexibleWorkGang* _workers;
5054 int _active_workers;
5055
5056 public:
5057 G1STWRefProcTaskExecutor(G1CollectedHeap* g1h,
5058 FlexibleWorkGang* workers,
5059 RefToScanQueueSet *task_queues,
5060 int n_workers) :
5061 _g1h(g1h),
5062 _queues(task_queues),
5063 _workers(workers),
5064 _active_workers(n_workers)
5065 {
5066 assert(n_workers > 0, "shouldn't call this otherwise");
5067 }
5068
5069 // Executes the given task using concurrent marking worker threads.
5070 virtual void execute(ProcessTask& task);
5071 virtual void execute(EnqueueTask& task);
5072 };
5073
5074 // Gang task for possibly parallel reference processing
5075
5076 class G1STWRefProcTaskProxy: public AbstractGangTask {
5077 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
5078 ProcessTask& _proc_task;
5079 G1CollectedHeap* _g1h;
5080 RefToScanQueueSet *_task_queues;
5081 ParallelTaskTerminator* _terminator;
5082
5083 public:
5084 G1STWRefProcTaskProxy(ProcessTask& proc_task,
5085 G1CollectedHeap* g1h,
5086 RefToScanQueueSet *task_queues,
5087 ParallelTaskTerminator* terminator) :
5088 AbstractGangTask("Process reference objects in parallel"),
5089 _proc_task(proc_task),
5090 _g1h(g1h),
5091 _task_queues(task_queues),
5092 _terminator(terminator)
5093 {}
5094
5095 virtual void work(uint worker_id) {
5096 // The reference processing task executed by a single worker.
5097 ResourceMark rm;
5098 HandleMark hm;
5099
5100 G1STWIsAliveClosure is_alive(_g1h);
5101
5102 G1ParScanThreadState pss(_g1h, worker_id);
5103
5104 G1ParScanHeapEvacClosure scan_evac_cl(_g1h, &pss, NULL);
5105 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL);
5106 G1ParScanPartialArrayClosure partial_scan_cl(_g1h, &pss, NULL);
5107
5108 pss.set_evac_closure(&scan_evac_cl);
5109 pss.set_evac_failure_closure(&evac_failure_cl);
5110 pss.set_partial_scan_closure(&partial_scan_cl);
5111
5112 G1ParScanExtRootClosure only_copy_non_heap_cl(_g1h, &pss, NULL);
5113 G1ParScanPermClosure only_copy_perm_cl(_g1h, &pss, NULL);
5114
5115 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL);
5116 G1ParScanAndMarkPermClosure copy_mark_perm_cl(_g1h, &pss, NULL);
5117
5118 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl;
5119 OopsInHeapRegionClosure* copy_perm_cl = &only_copy_perm_cl;
5120
5121 if (_g1h->g1_policy()->during_initial_mark_pause()) {
5122 // We also need to mark copied objects.
5123 copy_non_heap_cl = ©_mark_non_heap_cl;
5124 copy_perm_cl = ©_mark_perm_cl;
5125 }
5126
5127 // Keep alive closure.
5128 G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, copy_perm_cl, &pss);
5129
5130 // Complete GC closure
5131 G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _task_queues, _terminator);
5132
5133 // Call the reference processing task's work routine.
5134 _proc_task.work(worker_id, is_alive, keep_alive, drain_queue);
5135
5136 // Note we cannot assert that the refs array is empty here as not all
5137 // of the processing tasks (specifically phase2 - pp2_work) execute
5138 // the complete_gc closure (which ordinarily would drain the queue) so
5139 // the queue may not be empty.
5140 }
5141 };
5142
5143 // Driver routine for parallel reference processing.
5144 // Creates an instance of the ref processing gang
5145 // task and has the worker threads execute it.
5146 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) {
5147 assert(_workers != NULL, "Need parallel worker threads.");
5148
5149 ParallelTaskTerminator terminator(_active_workers, _queues);
5150 G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _queues, &terminator);
5151
5152 _g1h->set_par_threads(_active_workers);
5153 _workers->run_task(&proc_task_proxy);
5154 _g1h->set_par_threads(0);
5155 }
5156
5157 // Gang task for parallel reference enqueueing.
5158
5159 class G1STWRefEnqueueTaskProxy: public AbstractGangTask {
5160 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;
5161 EnqueueTask& _enq_task;
5162
5163 public:
5164 G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) :
5165 AbstractGangTask("Enqueue reference objects in parallel"),
5166 _enq_task(enq_task)
5167 { }
5168
5169 virtual void work(uint worker_id) {
5170 _enq_task.work(worker_id);
5171 }
5172 };
5173
5174 // Driver routine for parallel reference enqueing.
5175 // Creates an instance of the ref enqueueing gang
5176 // task and has the worker threads execute it.
5177
5178 void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) {
5179 assert(_workers != NULL, "Need parallel worker threads.");
5180
5181 G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task);
5182
5183 _g1h->set_par_threads(_active_workers);
5184 _workers->run_task(&enq_task_proxy);
5185 _g1h->set_par_threads(0);
5186 }
5187
5188 // End of weak reference support closures
5189
5190 // Abstract task used to preserve (i.e. copy) any referent objects
5191 // that are in the collection set and are pointed to by reference
5192 // objects discovered by the CM ref processor.
5193
5194 class G1ParPreserveCMReferentsTask: public AbstractGangTask {
5195 protected:
5196 G1CollectedHeap* _g1h;
5197 RefToScanQueueSet *_queues;
5198 ParallelTaskTerminator _terminator;
5199 uint _n_workers;
5200
5201 public:
5202 G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h,int workers, RefToScanQueueSet *task_queues) :
5203 AbstractGangTask("ParPreserveCMReferents"),
5204 _g1h(g1h),
5205 _queues(task_queues),
5206 _terminator(workers, _queues),
5207 _n_workers(workers)
5208 { }
5209
5210 void work(uint worker_id) {
5211 ResourceMark rm;
5212 HandleMark hm;
5213
5214 G1ParScanThreadState pss(_g1h, worker_id);
5215 G1ParScanHeapEvacClosure scan_evac_cl(_g1h, &pss, NULL);
5216 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL);
5217 G1ParScanPartialArrayClosure partial_scan_cl(_g1h, &pss, NULL);
5218
5219 pss.set_evac_closure(&scan_evac_cl);
5220 pss.set_evac_failure_closure(&evac_failure_cl);
5221 pss.set_partial_scan_closure(&partial_scan_cl);
5222
5223 assert(pss.refs()->is_empty(), "both queue and overflow should be empty");
5224
5225
5226 G1ParScanExtRootClosure only_copy_non_heap_cl(_g1h, &pss, NULL);
5227 G1ParScanPermClosure only_copy_perm_cl(_g1h, &pss, NULL);
5228
5229 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL);
5230 G1ParScanAndMarkPermClosure copy_mark_perm_cl(_g1h, &pss, NULL);
5231
5232 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl;
5233 OopsInHeapRegionClosure* copy_perm_cl = &only_copy_perm_cl;
5234
5235 if (_g1h->g1_policy()->during_initial_mark_pause()) {
5236 // We also need to mark copied objects.
5237 copy_non_heap_cl = ©_mark_non_heap_cl;
5238 copy_perm_cl = ©_mark_perm_cl;
5239 }
5240
5241 // Is alive closure
5242 G1AlwaysAliveClosure always_alive(_g1h);
5243
5244 // Copying keep alive closure. Applied to referent objects that need
5245 // to be copied.
5246 G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, copy_perm_cl, &pss);
5247
5248 ReferenceProcessor* rp = _g1h->ref_processor_cm();
5249
5250 uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q();
5251 uint stride = MIN2(MAX2(_n_workers, 1U), limit);
5252
5253 // limit is set using max_num_q() - which was set using ParallelGCThreads.
5254 // So this must be true - but assert just in case someone decides to
5255 // change the worker ids.
5256 assert(0 <= worker_id && worker_id < limit, "sanity");
5257 assert(!rp->discovery_is_atomic(), "check this code");
5258
5259 // Select discovered lists [i, i+stride, i+2*stride,...,limit)
5260 for (uint idx = worker_id; idx < limit; idx += stride) {
5261 DiscoveredList& ref_list = rp->discovered_refs()[idx];
5262
5263 DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive);
5264 while (iter.has_next()) {
5265 // Since discovery is not atomic for the CM ref processor, we
5266 // can see some null referent objects.
5267 iter.load_ptrs(DEBUG_ONLY(true));
5268 oop ref = iter.obj();
5269
5270 // This will filter nulls.
5271 if (iter.is_referent_alive()) {
5272 iter.make_referent_alive();
5273 }
5274 iter.move_to_next();
5275 }
5276 }
5277
5278 // Drain the queue - which may cause stealing
5279 G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _queues, &_terminator);
5280 drain_queue.do_void();
5281 // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure
5282 assert(pss.refs()->is_empty(), "should be");
5283 }
5284 };
5285
5286 // Weak Reference processing during an evacuation pause (part 1).
5287 void G1CollectedHeap::process_discovered_references() {
5288 double ref_proc_start = os::elapsedTime();
5289
5290 ReferenceProcessor* rp = _ref_processor_stw;
5291 assert(rp->discovery_enabled(), "should have been enabled");
5292
5293 // Any reference objects, in the collection set, that were 'discovered'
5294 // by the CM ref processor should have already been copied (either by
5295 // applying the external root copy closure to the discovered lists, or
5296 // by following an RSet entry).
5297 //
5298 // But some of the referents, that are in the collection set, that these
5299 // reference objects point to may not have been copied: the STW ref
5300 // processor would have seen that the reference object had already
5301 // been 'discovered' and would have skipped discovering the reference,
5302 // but would not have treated the reference object as a regular oop.
5303 // As a reult the copy closure would not have been applied to the
5304 // referent object.
5305 //
5306 // We need to explicitly copy these referent objects - the references
5307 // will be processed at the end of remarking.
5308 //
5309 // We also need to do this copying before we process the reference
5310 // objects discovered by the STW ref processor in case one of these
5311 // referents points to another object which is also referenced by an
5312 // object discovered by the STW ref processor.
5313
5314 uint active_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
5315 workers()->active_workers() : 1);
5316
5317 assert(!G1CollectedHeap::use_parallel_gc_threads() ||
5318 active_workers == workers()->active_workers(),
5319 "Need to reset active_workers");
5320
5321 set_par_threads(active_workers);
5322 G1ParPreserveCMReferentsTask keep_cm_referents(this, active_workers, _task_queues);
5323
5324 if (G1CollectedHeap::use_parallel_gc_threads()) {
5325 workers()->run_task(&keep_cm_referents);
5326 } else {
5327 keep_cm_referents.work(0);
5328 }
5329
5330 set_par_threads(0);
5331
5332 // Closure to test whether a referent is alive.
5333 G1STWIsAliveClosure is_alive(this);
5334
5335 // Even when parallel reference processing is enabled, the processing
5336 // of JNI refs is serial and performed serially by the current thread
5337 // rather than by a worker. The following PSS will be used for processing
5338 // JNI refs.
5339
5340 // Use only a single queue for this PSS.
5341 G1ParScanThreadState pss(this, 0);
5342
5343 // We do not embed a reference processor in the copying/scanning
5344 // closures while we're actually processing the discovered
5345 // reference objects.
5346 G1ParScanHeapEvacClosure scan_evac_cl(this, &pss, NULL);
5347 G1ParScanHeapEvacFailureClosure evac_failure_cl(this, &pss, NULL);
5348 G1ParScanPartialArrayClosure partial_scan_cl(this, &pss, NULL);
5349
5350 pss.set_evac_closure(&scan_evac_cl);
5351 pss.set_evac_failure_closure(&evac_failure_cl);
5352 pss.set_partial_scan_closure(&partial_scan_cl);
5353
5354 assert(pss.refs()->is_empty(), "pre-condition");
5355
5356 G1ParScanExtRootClosure only_copy_non_heap_cl(this, &pss, NULL);
5357 G1ParScanPermClosure only_copy_perm_cl(this, &pss, NULL);
5358
5359 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(this, &pss, NULL);
5360 G1ParScanAndMarkPermClosure copy_mark_perm_cl(this, &pss, NULL);
5361
5362 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl;
5363 OopsInHeapRegionClosure* copy_perm_cl = &only_copy_perm_cl;
5364
5365 if (_g1h->g1_policy()->during_initial_mark_pause()) {
5366 // We also need to mark copied objects.
5367 copy_non_heap_cl = ©_mark_non_heap_cl;
5368 copy_perm_cl = ©_mark_perm_cl;
5369 }
5370
5371 // Keep alive closure.
5372 G1CopyingKeepAliveClosure keep_alive(this, copy_non_heap_cl, copy_perm_cl, &pss);
5373
5374 // Serial Complete GC closure
5375 G1STWDrainQueueClosure drain_queue(this, &pss);
5376
5377 // Setup the soft refs policy...
5378 rp->setup_policy(false);
5379
5380 if (!rp->processing_is_mt()) {
5381 // Serial reference processing...
5382 rp->process_discovered_references(&is_alive,
5383 &keep_alive,
5384 &drain_queue,
5385 NULL);
5386 } else {
5387 // Parallel reference processing
5388 assert(rp->num_q() == active_workers, "sanity");
5389 assert(active_workers <= rp->max_num_q(), "sanity");
5390
5391 G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, active_workers);
5392 rp->process_discovered_references(&is_alive, &keep_alive, &drain_queue, &par_task_executor);
5393 }
5394
5395 // We have completed copying any necessary live referent objects
5396 // (that were not copied during the actual pause) so we can
5397 // retire any active alloc buffers
5398 pss.retire_alloc_buffers();
5399 assert(pss.refs()->is_empty(), "both queue and overflow should be empty");
5400
5401 double ref_proc_time = os::elapsedTime() - ref_proc_start;
5402 g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0);
5403 }
5404
5405 // Weak Reference processing during an evacuation pause (part 2).
5406 void G1CollectedHeap::enqueue_discovered_references() {
5407 double ref_enq_start = os::elapsedTime();
5408
5409 ReferenceProcessor* rp = _ref_processor_stw;
5410 assert(!rp->discovery_enabled(), "should have been disabled as part of processing");
5411
5412 // Now enqueue any remaining on the discovered lists on to
5413 // the pending list.
5414 if (!rp->processing_is_mt()) {
5415 // Serial reference processing...
5416 rp->enqueue_discovered_references();
5417 } else {
5418 // Parallel reference enqueuing
5419
5420 uint active_workers = (ParallelGCThreads > 0 ? workers()->active_workers() : 1);
5421 assert(active_workers == workers()->active_workers(),
5422 "Need to reset active_workers");
5423 assert(rp->num_q() == active_workers, "sanity");
5424 assert(active_workers <= rp->max_num_q(), "sanity");
5425
5426 G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, active_workers);
5427 rp->enqueue_discovered_references(&par_task_executor);
5428 }
5429
5430 rp->verify_no_references_recorded();
5431 assert(!rp->discovery_enabled(), "should have been disabled");
5432
5433 // FIXME
5434 // CM's reference processing also cleans up the string and symbol tables.
5435 // Should we do that here also? We could, but it is a serial operation
5436 // and could signicantly increase the pause time.
5437
5438 double ref_enq_time = os::elapsedTime() - ref_enq_start;
5439 g1_policy()->phase_times()->record_ref_enq_time(ref_enq_time * 1000.0);
5440 }
5441
5442 void G1CollectedHeap::evacuate_collection_set() {
5443 _expand_heap_after_alloc_failure = true;
5444 set_evacuation_failed(false);
5445
5446 g1_rem_set()->prepare_for_oops_into_collection_set_do();
5447 concurrent_g1_refine()->set_use_cache(false);
5448 concurrent_g1_refine()->clear_hot_cache_claimed_index();
5449
5450 uint n_workers;
5451 if (G1CollectedHeap::use_parallel_gc_threads()) {
5452 n_workers =
5453 AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
5454 workers()->active_workers(),
5455 Threads::number_of_non_daemon_threads());
5456 assert(UseDynamicNumberOfGCThreads ||
5457 n_workers == workers()->total_workers(),
5458 "If not dynamic should be using all the workers");
5459 workers()->set_active_workers(n_workers);
5460 set_par_threads(n_workers);
5461 } else {
5462 assert(n_par_threads() == 0,
5463 "Should be the original non-parallel value");
5464 n_workers = 1;
5465 }
5466
5467 G1ParTask g1_par_task(this, _task_queues);
5468
5469 init_for_evac_failure(NULL);
5470
5471 rem_set()->prepare_for_younger_refs_iterate(true);
5472
5473 assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty");
5474 double start_par_time_sec = os::elapsedTime();
5475 double end_par_time_sec;
5476
5477 {
5478 StrongRootsScope srs(this);
5479
5480 if (G1CollectedHeap::use_parallel_gc_threads()) {
5481 // The individual threads will set their evac-failure closures.
5482 if (ParallelGCVerbose) G1ParScanThreadState::print_termination_stats_hdr();
5483 // These tasks use ShareHeap::_process_strong_tasks
5484 assert(UseDynamicNumberOfGCThreads ||
5485 workers()->active_workers() == workers()->total_workers(),
5486 "If not dynamic should be using all the workers");
5487 workers()->run_task(&g1_par_task);
5488 } else {
5489 g1_par_task.set_for_termination(n_workers);
5490 g1_par_task.work(0);
5491 }
5492 end_par_time_sec = os::elapsedTime();
5493
5494 // Closing the inner scope will execute the destructor
5495 // for the StrongRootsScope object. We record the current
5496 // elapsed time before closing the scope so that time
5497 // taken for the SRS destructor is NOT included in the
5498 // reported parallel time.
5499 }
5500
5501 double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0;
5502 g1_policy()->phase_times()->record_par_time(par_time_ms);
5503
5504 double code_root_fixup_time_ms =
5505 (os::elapsedTime() - end_par_time_sec) * 1000.0;
5506 g1_policy()->phase_times()->record_code_root_fixup_time(code_root_fixup_time_ms);
5507
5508 set_par_threads(0);
5509
5510 // Process any discovered reference objects - we have
5511 // to do this _before_ we retire the GC alloc regions
5512 // as we may have to copy some 'reachable' referent
5513 // objects (and their reachable sub-graphs) that were
5514 // not copied during the pause.
5515 process_discovered_references();
5516
5517 // Weak root processing.
5518 // Note: when JSR 292 is enabled and code blobs can contain
5519 // non-perm oops then we will need to process the code blobs
5520 // here too.
5521 {
5522 G1STWIsAliveClosure is_alive(this);
5523 G1KeepAliveClosure keep_alive(this);
5524 JNIHandles::weak_oops_do(&is_alive, &keep_alive);
5525 }
5526
5527 release_gc_alloc_regions();
5528 g1_rem_set()->cleanup_after_oops_into_collection_set_do();
5529
5530 concurrent_g1_refine()->clear_hot_cache();
5531 concurrent_g1_refine()->set_use_cache(true);
5532
5533 finalize_for_evac_failure();
5534
5535 if (evacuation_failed()) {
5536 remove_self_forwarding_pointers();
5537 if (G1Log::finer()) {
5538 gclog_or_tty->print(" (to-space exhausted)");
5539 } else if (G1Log::fine()) {
5540 gclog_or_tty->print("--");
5541 }
5542 }
5543
5544 // Enqueue any remaining references remaining on the STW
5545 // reference processor's discovered lists. We need to do
5546 // this after the card table is cleaned (and verified) as
5547 // the act of enqueuing entries on to the pending list
5548 // will log these updates (and dirty their associated
5549 // cards). We need these updates logged to update any
5550 // RSets.
5551 enqueue_discovered_references();
5552
5553 if (G1DeferredRSUpdate) {
5554 RedirtyLoggedCardTableEntryFastClosure redirty;
5555 dirty_card_queue_set().set_closure(&redirty);
5556 dirty_card_queue_set().apply_closure_to_all_completed_buffers();
5557
5558 DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set();
5559 dcq.merge_bufferlists(&dirty_card_queue_set());
5560 assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed");
5561 }
5562 COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
5563 }
5564
5565 void G1CollectedHeap::free_region_if_empty(HeapRegion* hr,
5566 size_t* pre_used,
5567 FreeRegionList* free_list,
5568 OldRegionSet* old_proxy_set,
5569 HumongousRegionSet* humongous_proxy_set,
5570 HRRSCleanupTask* hrrs_cleanup_task,
5571 bool par) {
5572 if (hr->used() > 0 && hr->max_live_bytes() == 0 && !hr->is_young()) {
5573 if (hr->isHumongous()) {
5574 assert(hr->startsHumongous(), "we should only see starts humongous");
5575 free_humongous_region(hr, pre_used, free_list, humongous_proxy_set, par);
5576 } else {
5577 _old_set.remove_with_proxy(hr, old_proxy_set);
5578 free_region(hr, pre_used, free_list, par);
5579 }
5580 } else {
5581 hr->rem_set()->do_cleanup_work(hrrs_cleanup_task);
5582 }
5583 }
5584
5585 void G1CollectedHeap::free_region(HeapRegion* hr,
5586 size_t* pre_used,
5587 FreeRegionList* free_list,
5588 bool par) {
5589 assert(!hr->isHumongous(), "this is only for non-humongous regions");
5590 assert(!hr->is_empty(), "the region should not be empty");
5591 assert(free_list != NULL, "pre-condition");
5592
5593 *pre_used += hr->used();
5594 hr->hr_clear(par, true /* clear_space */);
5595 free_list->add_as_head(hr);
5596 }
5597
5598 void G1CollectedHeap::free_humongous_region(HeapRegion* hr,
5599 size_t* pre_used,
5600 FreeRegionList* free_list,
5601 HumongousRegionSet* humongous_proxy_set,
5602 bool par) {
5603 assert(hr->startsHumongous(), "this is only for starts humongous regions");
5604 assert(free_list != NULL, "pre-condition");
5605 assert(humongous_proxy_set != NULL, "pre-condition");
5606
5607 size_t hr_used = hr->used();
5608 size_t hr_capacity = hr->capacity();
5609 size_t hr_pre_used = 0;
5610 _humongous_set.remove_with_proxy(hr, humongous_proxy_set);
5611 hr->set_notHumongous();
5612 free_region(hr, &hr_pre_used, free_list, par);
5613
5614 uint i = hr->hrs_index() + 1;
5615 uint num = 1;
5616 while (i < n_regions()) {
5617 HeapRegion* curr_hr = region_at(i);
5618 if (!curr_hr->continuesHumongous()) {
5619 break;
5620 }
5621 curr_hr->set_notHumongous();
5622 free_region(curr_hr, &hr_pre_used, free_list, par);
5623 num += 1;
5624 i += 1;
5625 }
5626 assert(hr_pre_used == hr_used,
5627 err_msg("hr_pre_used: "SIZE_FORMAT" and hr_used: "SIZE_FORMAT" "
5628 "should be the same", hr_pre_used, hr_used));
5629 *pre_used += hr_pre_used;
5630 }
5631
5632 void G1CollectedHeap::update_sets_after_freeing_regions(size_t pre_used,
5633 FreeRegionList* free_list,
5634 OldRegionSet* old_proxy_set,
5635 HumongousRegionSet* humongous_proxy_set,
5636 bool par) {
5637 if (pre_used > 0) {
5638 Mutex* lock = (par) ? ParGCRareEvent_lock : NULL;
5639 MutexLockerEx x(lock, Mutex::_no_safepoint_check_flag);
5640 assert(_summary_bytes_used >= pre_used,
5641 err_msg("invariant: _summary_bytes_used: "SIZE_FORMAT" "
5642 "should be >= pre_used: "SIZE_FORMAT,
5643 _summary_bytes_used, pre_used));
5644 _summary_bytes_used -= pre_used;
5645 }
5646 if (free_list != NULL && !free_list->is_empty()) {
5647 MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag);
5648 _free_list.add_as_head(free_list);
5649 }
5650 if (old_proxy_set != NULL && !old_proxy_set->is_empty()) {
5651 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
5652 _old_set.update_from_proxy(old_proxy_set);
5653 }
5654 if (humongous_proxy_set != NULL && !humongous_proxy_set->is_empty()) {
5655 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
5656 _humongous_set.update_from_proxy(humongous_proxy_set);
5657 }
5658 }
5659
5660 class G1ParCleanupCTTask : public AbstractGangTask {
5661 CardTableModRefBS* _ct_bs;
5662 G1CollectedHeap* _g1h;
5663 HeapRegion* volatile _su_head;
5664 public:
5665 G1ParCleanupCTTask(CardTableModRefBS* ct_bs,
5666 G1CollectedHeap* g1h) :
5667 AbstractGangTask("G1 Par Cleanup CT Task"),
5668 _ct_bs(ct_bs), _g1h(g1h) { }
5669
5670 void work(uint worker_id) {
5671 HeapRegion* r;
5672 while (r = _g1h->pop_dirty_cards_region()) {
5673 clear_cards(r);
5674 }
5675 }
5676
5677 void clear_cards(HeapRegion* r) {
5678 // Cards of the survivors should have already been dirtied.
5679 if (!r->is_survivor()) {
5680 _ct_bs->clear(MemRegion(r->bottom(), r->end()));
5681 }
5682 }
5683 };
5684
5685 #ifndef PRODUCT
5686 class G1VerifyCardTableCleanup: public HeapRegionClosure {
5687 G1CollectedHeap* _g1h;
5688 CardTableModRefBS* _ct_bs;
5689 public:
5690 G1VerifyCardTableCleanup(G1CollectedHeap* g1h, CardTableModRefBS* ct_bs)
5691 : _g1h(g1h), _ct_bs(ct_bs) { }
5692 virtual bool doHeapRegion(HeapRegion* r) {
5693 if (r->is_survivor()) {
5694 _g1h->verify_dirty_region(r);
5695 } else {
5696 _g1h->verify_not_dirty_region(r);
5697 }
5698 return false;
5699 }
5700 };
5701
5702 void G1CollectedHeap::verify_not_dirty_region(HeapRegion* hr) {
5703 // All of the region should be clean.
5704 CardTableModRefBS* ct_bs = (CardTableModRefBS*)barrier_set();
5705 MemRegion mr(hr->bottom(), hr->end());
5706 ct_bs->verify_not_dirty_region(mr);
5707 }
5708
5709 void G1CollectedHeap::verify_dirty_region(HeapRegion* hr) {
5710 // We cannot guarantee that [bottom(),end()] is dirty. Threads
5711 // dirty allocated blocks as they allocate them. The thread that
5712 // retires each region and replaces it with a new one will do a
5713 // maximal allocation to fill in [pre_dummy_top(),end()] but will
5714 // not dirty that area (one less thing to have to do while holding
5715 // a lock). So we can only verify that [bottom(),pre_dummy_top()]
5716 // is dirty.
5717 CardTableModRefBS* ct_bs = (CardTableModRefBS*) barrier_set();
5718 MemRegion mr(hr->bottom(), hr->pre_dummy_top());
5719 ct_bs->verify_dirty_region(mr);
5720 }
5721
5722 void G1CollectedHeap::verify_dirty_young_list(HeapRegion* head) {
5723 CardTableModRefBS* ct_bs = (CardTableModRefBS*) barrier_set();
5724 for (HeapRegion* hr = head; hr != NULL; hr = hr->get_next_young_region()) {
5725 verify_dirty_region(hr);
5726 }
5727 }
5728
5729 void G1CollectedHeap::verify_dirty_young_regions() {
5730 verify_dirty_young_list(_young_list->first_region());
5731 verify_dirty_young_list(_young_list->first_survivor_region());
5732 }
5733 #endif
5734
5735 void G1CollectedHeap::cleanUpCardTable() {
5736 CardTableModRefBS* ct_bs = (CardTableModRefBS*) (barrier_set());
5737 double start = os::elapsedTime();
5738
5739 {
5740 // Iterate over the dirty cards region list.
5741 G1ParCleanupCTTask cleanup_task(ct_bs, this);
5742
5743 if (G1CollectedHeap::use_parallel_gc_threads()) {
5744 set_par_threads();
5745 workers()->run_task(&cleanup_task);
5746 set_par_threads(0);
5747 } else {
5748 while (_dirty_cards_region_list) {
5749 HeapRegion* r = _dirty_cards_region_list;
5750 cleanup_task.clear_cards(r);
5751 _dirty_cards_region_list = r->get_next_dirty_cards_region();
5752 if (_dirty_cards_region_list == r) {
5753 // The last region.
5754 _dirty_cards_region_list = NULL;
5755 }
5756 r->set_next_dirty_cards_region(NULL);
5757 }
5758 }
5759 #ifndef PRODUCT
5760 if (G1VerifyCTCleanup || VerifyAfterGC) {
5761 G1VerifyCardTableCleanup cleanup_verifier(this, ct_bs);
5762 heap_region_iterate(&cleanup_verifier);
5763 }
5764 #endif
5765 }
5766
5767 double elapsed = os::elapsedTime() - start;
5768 g1_policy()->phase_times()->record_clear_ct_time(elapsed * 1000.0);
5769 }
5770
5771 void G1CollectedHeap::free_collection_set(HeapRegion* cs_head) {
5772 size_t pre_used = 0;
5773 FreeRegionList local_free_list("Local List for CSet Freeing");
5774
5775 double young_time_ms = 0.0;
5776 double non_young_time_ms = 0.0;
5777
5778 // Since the collection set is a superset of the the young list,
5779 // all we need to do to clear the young list is clear its
5780 // head and length, and unlink any young regions in the code below
5781 _young_list->clear();
5782
5783 G1CollectorPolicy* policy = g1_policy();
5784
5785 double start_sec = os::elapsedTime();
5786 bool non_young = true;
5787
5788 HeapRegion* cur = cs_head;
5789 int age_bound = -1;
5790 size_t rs_lengths = 0;
5791
5792 while (cur != NULL) {
5793 assert(!is_on_master_free_list(cur), "sanity");
5794 if (non_young) {
5795 if (cur->is_young()) {
5796 double end_sec = os::elapsedTime();
5797 double elapsed_ms = (end_sec - start_sec) * 1000.0;
5798 non_young_time_ms += elapsed_ms;
5799
5800 start_sec = os::elapsedTime();
5801 non_young = false;
5802 }
5803 } else {
5804 if (!cur->is_young()) {
5805 double end_sec = os::elapsedTime();
5806 double elapsed_ms = (end_sec - start_sec) * 1000.0;
5807 young_time_ms += elapsed_ms;
5808
5809 start_sec = os::elapsedTime();
5810 non_young = true;
5811 }
5812 }
5813
5814 rs_lengths += cur->rem_set()->occupied();
5815
5816 HeapRegion* next = cur->next_in_collection_set();
5817 assert(cur->in_collection_set(), "bad CS");
5818 cur->set_next_in_collection_set(NULL);
5819 cur->set_in_collection_set(false);
5820
5821 if (cur->is_young()) {
5822 int index = cur->young_index_in_cset();
5823 assert(index != -1, "invariant");
5824 assert((uint) index < policy->young_cset_region_length(), "invariant");
5825 size_t words_survived = _surviving_young_words[index];
5826 cur->record_surv_words_in_group(words_survived);
5827
5828 // At this point the we have 'popped' cur from the collection set
5829 // (linked via next_in_collection_set()) but it is still in the
5830 // young list (linked via next_young_region()). Clear the
5831 // _next_young_region field.
5832 cur->set_next_young_region(NULL);
5833 } else {
5834 int index = cur->young_index_in_cset();
5835 assert(index == -1, "invariant");
5836 }
5837
5838 assert( (cur->is_young() && cur->young_index_in_cset() > -1) ||
5839 (!cur->is_young() && cur->young_index_in_cset() == -1),
5840 "invariant" );
5841
5842 if (!cur->evacuation_failed()) {
5843 MemRegion used_mr = cur->used_region();
5844
5845 // And the region is empty.
5846 assert(!used_mr.is_empty(), "Should not have empty regions in a CS.");
5847 free_region(cur, &pre_used, &local_free_list, false /* par */);
5848 } else {
5849 cur->uninstall_surv_rate_group();
5850 if (cur->is_young()) {
5851 cur->set_young_index_in_cset(-1);
5852 }
5853 cur->set_not_young();
5854 cur->set_evacuation_failed(false);
5855 // The region is now considered to be old.
5856 _old_set.add(cur);
5857 }
5858 cur = next;
5859 }
5860
5861 policy->record_max_rs_lengths(rs_lengths);
5862 policy->cset_regions_freed();
5863
5864 double end_sec = os::elapsedTime();
5865 double elapsed_ms = (end_sec - start_sec) * 1000.0;
5866
5867 if (non_young) {
5868 non_young_time_ms += elapsed_ms;
5869 } else {
5870 young_time_ms += elapsed_ms;
5871 }
5872
5873 update_sets_after_freeing_regions(pre_used, &local_free_list,
5874 NULL /* old_proxy_set */,
5875 NULL /* humongous_proxy_set */,
5876 false /* par */);
5877 policy->phase_times()->record_young_free_cset_time_ms(young_time_ms);
5878 policy->phase_times()->record_non_young_free_cset_time_ms(non_young_time_ms);
5879 }
5880
5881 // This routine is similar to the above but does not record
5882 // any policy statistics or update free lists; we are abandoning
5883 // the current incremental collection set in preparation of a
5884 // full collection. After the full GC we will start to build up
5885 // the incremental collection set again.
5886 // This is only called when we're doing a full collection
5887 // and is immediately followed by the tearing down of the young list.
5888
5889 void G1CollectedHeap::abandon_collection_set(HeapRegion* cs_head) {
5890 HeapRegion* cur = cs_head;
5891
5892 while (cur != NULL) {
5893 HeapRegion* next = cur->next_in_collection_set();
5894 assert(cur->in_collection_set(), "bad CS");
5895 cur->set_next_in_collection_set(NULL);
5896 cur->set_in_collection_set(false);
5897 cur->set_young_index_in_cset(-1);
5898 cur = next;
5899 }
5900 }
5901
5902 void G1CollectedHeap::set_free_regions_coming() {
5903 if (G1ConcRegionFreeingVerbose) {
5904 gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : "
5905 "setting free regions coming");
5906 }
5907
5908 assert(!free_regions_coming(), "pre-condition");
5909 _free_regions_coming = true;
5910 }
5911
5912 void G1CollectedHeap::reset_free_regions_coming() {
5913 assert(free_regions_coming(), "pre-condition");
5914
5915 {
5916 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
5917 _free_regions_coming = false;
5918 SecondaryFreeList_lock->notify_all();
5919 }
5920
5921 if (G1ConcRegionFreeingVerbose) {
5922 gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : "
5923 "reset free regions coming");
5924 }
5925 }
5926
5927 void G1CollectedHeap::wait_while_free_regions_coming() {
5928 // Most of the time we won't have to wait, so let's do a quick test
5929 // first before we take the lock.
5930 if (!free_regions_coming()) {
5931 return;
5932 }
5933
5934 if (G1ConcRegionFreeingVerbose) {
5935 gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : "
5936 "waiting for free regions");
5937 }
5938
5939 {
5940 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
5941 while (free_regions_coming()) {
5942 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
5943 }
5944 }
5945
5946 if (G1ConcRegionFreeingVerbose) {
5947 gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : "
5948 "done waiting for free regions");
5949 }
5950 }
5951
5952 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) {
5953 assert(heap_lock_held_for_gc(),
5954 "the heap lock should already be held by or for this thread");
5955 _young_list->push_region(hr);
5956 }
5957
5958 class NoYoungRegionsClosure: public HeapRegionClosure {
5959 private:
5960 bool _success;
5961 public:
5962 NoYoungRegionsClosure() : _success(true) { }
5963 bool doHeapRegion(HeapRegion* r) {
5964 if (r->is_young()) {
5965 gclog_or_tty->print_cr("Region ["PTR_FORMAT", "PTR_FORMAT") tagged as young",
5966 r->bottom(), r->end());
5967 _success = false;
5968 }
5969 return false;
5970 }
5971 bool success() { return _success; }
5972 };
5973
5974 bool G1CollectedHeap::check_young_list_empty(bool check_heap, bool check_sample) {
5975 bool ret = _young_list->check_list_empty(check_sample);
5976
5977 if (check_heap) {
5978 NoYoungRegionsClosure closure;
5979 heap_region_iterate(&closure);
5980 ret = ret && closure.success();
5981 }
5982
5983 return ret;
5984 }
5985
5986 class TearDownRegionSetsClosure : public HeapRegionClosure {
5987 private:
5988 OldRegionSet *_old_set;
5989
5990 public:
5991 TearDownRegionSetsClosure(OldRegionSet* old_set) : _old_set(old_set) { }
5992
5993 bool doHeapRegion(HeapRegion* r) {
5994 if (r->is_empty()) {
5995 // We ignore empty regions, we'll empty the free list afterwards
5996 } else if (r->is_young()) {
5997 // We ignore young regions, we'll empty the young list afterwards
5998 } else if (r->isHumongous()) {
5999 // We ignore humongous regions, we're not tearing down the
6000 // humongous region set
6001 } else {
6002 // The rest should be old
6003 _old_set->remove(r);
6004 }
6005 return false;
6006 }
6007
6008 ~TearDownRegionSetsClosure() {
6009 assert(_old_set->is_empty(), "post-condition");
6010 }
6011 };
6012
6013 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) {
6014 assert_at_safepoint(true /* should_be_vm_thread */);
6015
6016 if (!free_list_only) {
6017 TearDownRegionSetsClosure cl(&_old_set);
6018 heap_region_iterate(&cl);
6019
6020 // Need to do this after the heap iteration to be able to
6021 // recognize the young regions and ignore them during the iteration.
6022 _young_list->empty_list();
6023 }
6024 _free_list.remove_all();
6025 }
6026
6027 class RebuildRegionSetsClosure : public HeapRegionClosure {
6028 private:
6029 bool _free_list_only;
6030 OldRegionSet* _old_set;
6031 FreeRegionList* _free_list;
6032 size_t _total_used;
6033
6034 public:
6035 RebuildRegionSetsClosure(bool free_list_only,
6036 OldRegionSet* old_set, FreeRegionList* free_list) :
6037 _free_list_only(free_list_only),
6038 _old_set(old_set), _free_list(free_list), _total_used(0) {
6039 assert(_free_list->is_empty(), "pre-condition");
6040 if (!free_list_only) {
6041 assert(_old_set->is_empty(), "pre-condition");
6042 }
6043 }
6044
6045 bool doHeapRegion(HeapRegion* r) {
6046 if (r->continuesHumongous()) {
6047 return false;
6048 }
6049
6050 if (r->is_empty()) {
6051 // Add free regions to the free list
6052 _free_list->add_as_tail(r);
6053 } else if (!_free_list_only) {
6054 assert(!r->is_young(), "we should not come across young regions");
6055
6056 if (r->isHumongous()) {
6057 // We ignore humongous regions, we left the humongous set unchanged
6058 } else {
6059 // The rest should be old, add them to the old set
6060 _old_set->add(r);
6061 }
6062 _total_used += r->used();
6063 }
6064
6065 return false;
6066 }
6067
6068 size_t total_used() {
6069 return _total_used;
6070 }
6071 };
6072
6073 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) {
6074 assert_at_safepoint(true /* should_be_vm_thread */);
6075
6076 RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_free_list);
6077 heap_region_iterate(&cl);
6078
6079 if (!free_list_only) {
6080 _summary_bytes_used = cl.total_used();
6081 }
6082 assert(_summary_bytes_used == recalculate_used(),
6083 err_msg("inconsistent _summary_bytes_used, "
6084 "value: "SIZE_FORMAT" recalculated: "SIZE_FORMAT,
6085 _summary_bytes_used, recalculate_used()));
6086 }
6087
6088 void G1CollectedHeap::set_refine_cte_cl_concurrency(bool concurrent) {
6089 _refine_cte_cl->set_concurrent(concurrent);
6090 }
6091
6092 bool G1CollectedHeap::is_in_closed_subset(const void* p) const {
6093 HeapRegion* hr = heap_region_containing(p);
6094 if (hr == NULL) {
6095 return is_in_permanent(p);
6096 } else {
6097 return hr->is_in(p);
6098 }
6099 }
6100
6101 // Methods for the mutator alloc region
6102
6103 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size,
6104 bool force) {
6105 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6106 assert(!force || g1_policy()->can_expand_young_list(),
6107 "if force is true we should be able to expand the young list");
6108 bool young_list_full = g1_policy()->is_young_list_full();
6109 if (force || !young_list_full) {
6110 HeapRegion* new_alloc_region = new_region(word_size,
6111 false /* do_expand */);
6112 if (new_alloc_region != NULL) {
6113 set_region_short_lived_locked(new_alloc_region);
6114 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Eden, young_list_full);
6115 return new_alloc_region;
6116 }
6117 }
6118 return NULL;
6119 }
6120
6121 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region,
6122 size_t allocated_bytes) {
6123 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6124 assert(alloc_region->is_young(), "all mutator alloc regions should be young");
6125
6126 g1_policy()->add_region_to_incremental_cset_lhs(alloc_region);
6127 _summary_bytes_used += allocated_bytes;
6128 _hr_printer.retire(alloc_region);
6129 // We update the eden sizes here, when the region is retired,
6130 // instead of when it's allocated, since this is the point that its
6131 // used space has been recored in _summary_bytes_used.
6132 g1mm()->update_eden_size();
6133 }
6134
6135 HeapRegion* MutatorAllocRegion::allocate_new_region(size_t word_size,
6136 bool force) {
6137 return _g1h->new_mutator_alloc_region(word_size, force);
6138 }
6139
6140 void G1CollectedHeap::set_par_threads() {
6141 // Don't change the number of workers. Use the value previously set
6142 // in the workgroup.
6143 assert(G1CollectedHeap::use_parallel_gc_threads(), "shouldn't be here otherwise");
6144 uint n_workers = workers()->active_workers();
6145 assert(UseDynamicNumberOfGCThreads ||
6146 n_workers == workers()->total_workers(),
6147 "Otherwise should be using the total number of workers");
6148 if (n_workers == 0) {
6149 assert(false, "Should have been set in prior evacuation pause.");
6150 n_workers = ParallelGCThreads;
6151 workers()->set_active_workers(n_workers);
6152 }
6153 set_par_threads(n_workers);
6154 }
6155
6156 void MutatorAllocRegion::retire_region(HeapRegion* alloc_region,
6157 size_t allocated_bytes) {
6158 _g1h->retire_mutator_alloc_region(alloc_region, allocated_bytes);
6159 }
6160
6161 // Methods for the GC alloc regions
6162
6163 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size,
6164 uint count,
6165 GCAllocPurpose ap) {
6166 assert(FreeList_lock->owned_by_self(), "pre-condition");
6167
6168 if (count < g1_policy()->max_regions(ap)) {
6169 HeapRegion* new_alloc_region = new_region(word_size,
6170 true /* do_expand */);
6171 if (new_alloc_region != NULL) {
6172 // We really only need to do this for old regions given that we
6173 // should never scan survivors. But it doesn't hurt to do it
6174 // for survivors too.
6175 new_alloc_region->set_saved_mark();
6176 if (ap == GCAllocForSurvived) {
6177 new_alloc_region->set_survivor();
6178 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Survivor);
6179 } else {
6180 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Old);
6181 }
6182 bool during_im = g1_policy()->during_initial_mark_pause();
6183 new_alloc_region->note_start_of_copying(during_im);
6184 return new_alloc_region;
6185 } else {
6186 g1_policy()->note_alloc_region_limit_reached(ap);
6187 }
6188 }
6189 return NULL;
6190 }
6191
6192 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region,
6193 size_t allocated_bytes,
6194 GCAllocPurpose ap) {
6195 bool during_im = g1_policy()->during_initial_mark_pause();
6196 alloc_region->note_end_of_copying(during_im);
6197 g1_policy()->record_bytes_copied_during_gc(allocated_bytes);
6198 if (ap == GCAllocForSurvived) {
6199 young_list()->add_survivor_region(alloc_region);
6200 } else {
6201 _old_set.add(alloc_region);
6202 }
6203 _hr_printer.retire(alloc_region);
6204 }
6205
6206 HeapRegion* SurvivorGCAllocRegion::allocate_new_region(size_t word_size,
6207 bool force) {
6208 assert(!force, "not supported for GC alloc regions");
6209 return _g1h->new_gc_alloc_region(word_size, count(), GCAllocForSurvived);
6210 }
6211
6212 void SurvivorGCAllocRegion::retire_region(HeapRegion* alloc_region,
6213 size_t allocated_bytes) {
6214 _g1h->retire_gc_alloc_region(alloc_region, allocated_bytes,
6215 GCAllocForSurvived);
6216 }
6217
6218 HeapRegion* OldGCAllocRegion::allocate_new_region(size_t word_size,
6219 bool force) {
6220 assert(!force, "not supported for GC alloc regions");
6221 return _g1h->new_gc_alloc_region(word_size, count(), GCAllocForTenured);
6222 }
6223
6224 void OldGCAllocRegion::retire_region(HeapRegion* alloc_region,
6225 size_t allocated_bytes) {
6226 _g1h->retire_gc_alloc_region(alloc_region, allocated_bytes,
6227 GCAllocForTenured);
6228 }
6229 // Heap region set verification
6230
6231 class VerifyRegionListsClosure : public HeapRegionClosure {
6232 private:
6233 FreeRegionList* _free_list;
6234 OldRegionSet* _old_set;
6235 HumongousRegionSet* _humongous_set;
6236 uint _region_count;
6237
6238 public:
6239 VerifyRegionListsClosure(OldRegionSet* old_set,
6240 HumongousRegionSet* humongous_set,
6241 FreeRegionList* free_list) :
6242 _old_set(old_set), _humongous_set(humongous_set),
6243 _free_list(free_list), _region_count(0) { }
6244
6245 uint region_count() { return _region_count; }
6246
6247 bool doHeapRegion(HeapRegion* hr) {
6248 _region_count += 1;
6249
6250 if (hr->continuesHumongous()) {
6251 return false;
6252 }
6253
6254 if (hr->is_young()) {
6255 // TODO
6256 } else if (hr->startsHumongous()) {
6257 _humongous_set->verify_next_region(hr);
6258 } else if (hr->is_empty()) {
6259 _free_list->verify_next_region(hr);
6260 } else {
6261 _old_set->verify_next_region(hr);
6262 }
6263 return false;
6264 }
6265 };
6266
6267 HeapRegion* G1CollectedHeap::new_heap_region(uint hrs_index,
6268 HeapWord* bottom) {
6269 HeapWord* end = bottom + HeapRegion::GrainWords;
6270 MemRegion mr(bottom, end);
6271 assert(_g1_reserved.contains(mr), "invariant");
6272 // This might return NULL if the allocation fails
6273 return new HeapRegion(hrs_index, _bot_shared, mr, true /* is_zeroed */);
6274 }
6275
6276 void G1CollectedHeap::verify_region_sets() {
6277 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6278
6279 // First, check the explicit lists.
6280 _free_list.verify();
6281 {
6282 // Given that a concurrent operation might be adding regions to
6283 // the secondary free list we have to take the lock before
6284 // verifying it.
6285 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6286 _secondary_free_list.verify();
6287 }
6288 _old_set.verify();
6289 _humongous_set.verify();
6290
6291 // If a concurrent region freeing operation is in progress it will
6292 // be difficult to correctly attributed any free regions we come
6293 // across to the correct free list given that they might belong to
6294 // one of several (free_list, secondary_free_list, any local lists,
6295 // etc.). So, if that's the case we will skip the rest of the
6296 // verification operation. Alternatively, waiting for the concurrent
6297 // operation to complete will have a non-trivial effect on the GC's
6298 // operation (no concurrent operation will last longer than the
6299 // interval between two calls to verification) and it might hide
6300 // any issues that we would like to catch during testing.
6301 if (free_regions_coming()) {
6302 return;
6303 }
6304
6305 // Make sure we append the secondary_free_list on the free_list so
6306 // that all free regions we will come across can be safely
6307 // attributed to the free_list.
6308 append_secondary_free_list_if_not_empty_with_lock();
6309
6310 // Finally, make sure that the region accounting in the lists is
6311 // consistent with what we see in the heap.
6312 _old_set.verify_start();
6313 _humongous_set.verify_start();
6314 _free_list.verify_start();
6315
6316 VerifyRegionListsClosure cl(&_old_set, &_humongous_set, &_free_list);
6317 heap_region_iterate(&cl);
6318
6319 _old_set.verify_end();
6320 _humongous_set.verify_end();
6321 _free_list.verify_end();
6322 }